Find the exact value pf cos 2x if sin x = - 4/5 (Quadrant III)

Answers

Answer 1

Answer:

[tex]\displaystyle \cos(2x)=-\frac{7}{25}[/tex]

Step-by-step explanation:

We want to find:

[tex]\displaystyle \cos(2x)\text{ given that }\sin(x)=-\frac{4}{5}[/tex]

And x is in QIII.

Recall that sine is the ratio of the opposite side to the hypotenuse.

Therefore, the adjacent side is (we can ignore the negative for now).

[tex]a=\sqrt{5^2-4^2}=\sqrt{25-16}=\sqrt{9}=3[/tex]

So, the adjacent side is 3, the opposite side is 4, and the hypotenuse is 5.

Using the double angle identity, we can rewrite:

[tex]\cos(2x)=\cos^2(x)-\sin^2(x)[/tex]

Since x is in QIII, cosine is positive, sine is negative, and tangent is negative.

Using the above values, we can conclude that:

[tex]\displaystyle \cos(x)=\frac{3}{5}\text{ and } \sin(x)=-\frac{4}{5}[/tex]

Substitute:

[tex]\displaystyle \cos(2x)=\Big(\frac{3}{5}\Big)^2-\Big(-\frac{4}{5}\Big)^2[/tex]

Evaluate:

[tex]\displaystyle \cos(2x)=\frac{9}{25}-\frac{16}{25}=-\frac{7}{25}[/tex]


Related Questions

Identify the slope and y intercept (m= and b= ) y=-4xt6;

Answers

Answer:

y=b slope= 4/1

Step-by-step explanation:

Answer:

m=-4, b=6

Step-by-step explanation:

y=-4x+6

y=mx+b where m=slope and b=y-intercept

PLEASE PLEASE HELP. I’ve wasted so many points on this problem :(

Answers

Answer:

13 cm

Step-by-step explanation:

A^2+12^2=15^2

A^2+144=225

A^2=81

A=9

9x2=18

31-18=13 cm

Find the perimeter of a rectangle whose width is 3 cm and whose diagonal is 3 √5 cm long.

A^2+3^2=3√5^2

A^2+9=45

A^2=36

A=6

3+3+6+6=18 cm

help me I just need this please ​

Answers

Answer:

160:140

Step-by-step explanation:

8+7 = 15

60000/15 = 4000

4000/200=20

therfore the dimensions are 20 times the amount

8x 20 = 160

7x 20 = 140

I'll give brainliest ​

Answers

Answer:

its 2/3

my bad

What is the equation of the line in y=mx+b format?

Answers

Y=mx+b

Y=1/2x+ -1

Or

Y=1/2x-1

Graph the following word problem and then write an equation: Jamal started with $4 in his savings and makes an additional $3 per week.

Answers

Answer:

use desmos

Step-by-step explanation:

put y=3x+4 and make a graph from that its really helpful trust me

EVERYONE PLZ PLZ PLZ ANSWER THIS QUESTION

Answers

Answer:

the answer is definitely c

Answer:

C

Step-by-step explanation:

Hope this helps! Have a nice day :D

-7x-2y = -13
x – 2y = 11

Answers

-7x -2y= -13
-x + 2y= -11
-8x=-24
x=3

(3) - 2y= 11
-2y= 8
y= -4

(3,-4)

Can somebody plz help answer the rest of these questions correctly (only if u done this before) thx :3

WILL MARK BRAINLIEST WHOEVER ANSWERS FIRST :SD

Answers

Answer:

9. 16.34

10. 51.84

11. 20.11

12. 76.03

13. 64.09

just look up circumference of a circle and you should be able to put the radius in the first thing that pops up :)

Which statement best uses this information to explain why the AA criterion can be used to prove ABC~DBE

Answers

Answer:b

Step-by-step explanation:

Answer: B

Step-by-step explanation:

A pallet weighs 475 pounds when it has 25 cases of soda on it.
Each case of soda weighs 19 pounds.
Write a linear equation in point-slope form that will give the weight in pounds, y, for
any number of cases of soda, x.

Answers

Answer:

y=25x+19

Step-by-step explanation:

you take the number of cases and add 19 to it then you have your y-intercept making your answer y=25x+19

Answer:

y – 475 = 19 (x – 25)

Step-by-step explanation:

How do you do 5a) and 5b)????? Please help!!!!

Answers

Answer:

[tex]21.0 { { {1221220 = 223jn}^{n \: \: \: \: \: \: \: \: \: \: \: \: \tan( \beta \beta \beta \beta \beta \beta \pi\pi) } }^{2} }^{2} \times \frac{?}{?} [/tex]

Answer:

31° F and 67° F

Step-by-step explanation:

(a)

When t = 0 then

f(0) = 31 + [tex]\frac{0}{100}[/tex] = 31 + 0 = 31° F

(b)

When t = 10 , then

f(10) = 31 + [tex]\frac{40(10^3)}{10^3+100}[/tex] = 31 + [tex]\frac{40000}{1100}[/tex] = 31 + 36.36... ≈ 67° F

So, I think the Knave of Spades is telling the truth because he wasn't accused of anything but im not sure. Brainliest goes to whoever answers the question properly :>

Answers

Answer:

B

Step-by-step explanation:

It all starts whether the Knave of Hearts tells the truth or not. You can decide yourself.

Hearts: H

Clubs: C

Diamonds: D

Spades: S

If H lies, C tells the truth, therefor D lies. So S tells the truth

If H tells the truth, C lies. Therefore D tells the truth and S lies

Answer:

2

Step-by-step explanation:

If the knave of hearts did steal the tarts, then the knave of clubs is lying saying that the knave of hearts is lying which mean the knave of diamonds is actually telling the truth when the knave of clubs said the knave of diamonds is lying they are therefore lying.

So in the question may be knave of hearts and Knave of diamonds may be telling the truth OR knave of clubs and knave of spades are telling the truth.

In conclusion, Alice stole the tarts xoxo

please answer will give brainliest

Answers

Answer:

50 im sorry if im wrong

Step-by-step explanation:

Answer:

225

Step-by-step explanation:

15 * 15 = 225

225 / 2 =

Za 30 dag żurawiny zapłacono 9,75zł. Oceń prawdziwość każdego zdania.

Answers

Step-by-step explanation:

Odpowiedź:

9.75zł :3 = 3.25zł

3.25zł x 4 = 13zł - Prawda

3.25zł x 10 = 32.50zł - Prawda

Liczę na najlepsze.

x/7 - 3 is greater than or less than 7

Answers

Answer:

less than

Step-by-step explanation:

pls mark brainliest

hope this helps

what is 4,390.44 + 8.399, and show work pls

Answers

Answer:

4,398.839

Step-by-step explanation:

4,390.440 + 8.399=x

.000+.009=.009

.04+.09=.13

.4+.3=.7

.009+.13+.7=0.839

---------------------------

4390+8=4398

----------------------------

4398+0.839=4398.839

how many yards
carpeting is needed to cover a 60 feet length room and 40 feet width ​

Answers

Answer:

[tex]266[/tex] [tex]\frac{2}{3}[/tex] [tex]yards[/tex]

Step-by-step explanation:

1. Approach

First, convert the dimensions of the room from feet to yards. Remember, the conversion rate between feet and yards is, [tex]3feet=1yard[/tex]. Next, find the area of the room by multiplying the length by the width.

2. Convert the unit of measurement

The measurement unit is given in feet, one must convert it into yards. The conversion rate between yards and feet is, [tex]3feet=1yard[/tex].

[tex]60feet=20yards\\\\40feet=13\frac{1}{3}yards[/tex]

3. Find the area of the room

Now multiply the length by the width to find the area of the room.

[tex]20yards*13\frac{1}{3}yrads\\\\= 20 * \frac{40}{3}\\\\=\frac{800}{3}\\\\= 266\frac{2}{3}_{.}yards^{2}[/tex]

Which is the right answer

Answers

Answer:

C

Step-by-step explanation:

Considering the length of the triangle, I believe the answer is c.

10
Tara is playing a party game in which a tiny ball is
dropped into a rectangular box. To win the game, she
must guess where the ball will stop. What should she
guess to maximize her chances of winning?
scribes the likelihood of the ball
quare or rectangular shaped area?
square
circle
triangle
shaded area
4

Answers

Answer:

1. Shaded Area 2. Unlikely

Step-by-step explanation:

edge2021

I am stuck with the above question, please help

Answers

Answer:

D  

Step-by-step explanation:

Two lines are parallel if they have the same slope.

the given equation is in the form

y=mx+b

where

m=-5/2

b=-7

m is the slope.  You can see this by noting that if you increase x by 1 you increase y by m.

So, in this case, you are looking for a line with slope of -5/2.

You can solve each of the choice equations for y to see which one has the right slope.

A: y=(2/5)x-6   no good

B: y=-(2/5)x-1   no good

C: y=(5/2)x-4   no good

D: y=-(5/2)x-4  GOOD

Multiplying polynomials

Answers

Answer:

multiply each term in one polynomial by each term in the other polynomial. add those answers together, and simplify if needed.

Step-by-step explanation:

The circumference of a circle is the around it?

Answers

Answer:

Yes

Step-by-step explanation:

cube root(8+ 3 root 21)+ cube root (8-3 root 21)
plese give good answer with explanation or I will report

Answers

Answer:

[tex]\sqrt[3]{8+3\sqrt{21} } + \sqrt[3]{8-3\sqrt{21} }[/tex] = 1

Step-by-step explanation:

Given[tex]\sqrt[3]{8+3\sqrt{21} } + \sqrt[3]{8-3\sqrt{21} }[/tex]To find The value of the expressionSolution

Let's rewrite the given as:

[tex]\sqrt[3]{3\sqrt{21} + 8} - \sqrt[3]{3\sqrt{21} - 8}[/tex]

Let the value is m and the expressions under 3rd roots are a and b, then we have

a = 3√21 + 8, b = 3√21 - 8m = ∛a - ∛b

Cube the both sides:

m³ = (∛a - ∛b)³m³ = a - b - 3[tex]\sqrt[3]{a^2b}[/tex] + 3[tex]\sqrt[3]{ab^2}[/tex]

Simplify in bits:

a - b = 3√21 + 8 - 3√21 + 8 = 16ab = (3√21 + 8)(3√21 - 8) = 9*21 - 64 = 125∛ab = ∛125 = 5

So the expression becomes:

m³ = 16 - 3[tex]\sqrt[3]{125a} + \sqrt[3]{125b}[/tex]m³ = 16 - 15∛a + 15∛bm³ = 16 - 15(∛a - ∛b)m³ = 16 - 15m

Solve for m:

m³ + 15m - 16 = 0m³ - 1 + 15m - 15 = 0(m - 1)(m² + m + 1) + 15(m - 1) = 0(m - 1)(m² + m + 16) = 0m - 1 = 0, m² + m + 16 = 0m = 1 is the only real root, the quadratic equation has no real roots

The answer is 1

is (0,-4)a solution ?
Please help :/ marked brainly

Answers

Answer:

Not enough informations

Answer:

no its -4

Step-by-step explanation:

2(8s+9)+–2(2s–3)?
answer
now
please
ill
give
branielest
if
correct

Answers

Answer:

[tex]12s+24[/tex]

Step-by-step explanation:

Distribute this and you get [tex]16s + 18 -4s + 6[/tex].

This simplifies to [tex]12s+24[/tex].

1. I have a tablespoon, but I need a teaspoon. What do I do?

2. I have a 2 cup measuring cup and need 1 1/4 cup mil and 1/2 cup of vegetable oil. How far do I fill it up if I’m measuring together?


I only need help with these two, my brain went completely blank while solving these.

Answers

Answer:

Step-by-step explanation:

1 tablespoon = 3 teaspoons

You need to fill the tablespoon a third full. Not accurate, but that's what you have to do.

:::::

1¼ + ½ = 1¾

you need to fill the 2 cup measuring cup ⅞ full to get 1¾ cups.

1. Fill the tablespoon only 1/3 full
2. Fill it up 1 3/4 full

List all the 4-digit even numbers that can be created by rearranging these number tiles.
3
4
7
2

Answers

Answer:

3472

3274

3742

3724

7342

7324

7234

7432

4372

4732

2374

2734

i found this much

These are the 12 possible 4-digit even numbers that can be created by rearranging the number tiles (3, 4, 7, 2).

To create 4-digit even numbers by rearranging the given number tiles (3, 4, 7, 2), we need to consider the following conditions:

The last digit must be an even number (2 or 4).The thousand digits cannot be 0.

Considering these conditions, the possible 4-digit even numbers that can be formed are:

   2347

   2374

   3247

   3274

   3427

   3472

   4237

   4273

   4327

   4372

   4723

   4732

These are the 12 possible 4-digit even numbers that can be created by rearranging the number tiles (3, 4, 7, 2).

Learn more about the even numbers here:

https://brainly.com/question/2142825

#SPJ4

look at this i think this boy likes me

Answers

Answer:

talk to him

Step-by-step explanation:

he def likes you lmazo

Need help will give you the brainliest

Answers

Answer:

The answer is 3v + 5w

Step-by-step explanation:

simple add how many v's there are which are 3 so its 3v and count how many w's there are which is 5 so 5w all together is 3v+ 5w

hope this helps!

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