All categories

3 years ago

Prove that cos 3A = cos (2A+A)

Mathematics

2 answers:

Blababa [14]3 years ago

6 0

Not sure what the question is, but I guess it's to prove that

$\cos3A=4\cos^3A-3\cos A$

Expand the left side as

$\cos3A=\cos(2A+A)=\cos2A\cos A-\sin2A\sin A$

and use the double angle identities to write

$\cos3A=(\cos^2A-\sin^2A)\cos A-2\sin^2A\cos A$

$\cos3A=\cos^3A-3\sin^2A\cos A$

Recall the Pythagorean identity:

$\cos3A=\cos^3A-3(1-\cos^2A)\cos A$

$\cos3A=\cos^3A-3\cos A+3\cos^3A$

$\implies\cos3A=4\cos^3A-3\cos A$

as required.

olga55 [171]3 years ago

4 0

Answer:

you useless coomstain

Step-by-step explanation:

You might be interested in

Which number is rational?

Vitek1552 [10]

<span>The answer is D.

Don't be fooled sqrt(10) goes on for many many places and if you know the 20th digit is a 9 you have a 1 in 10 chance of predicting what the next digit is. The same is true for pi and sqrt(2). The sqrt root of 16 is 4 which is rational. It could be - 4 which is still rational. The other 3 go on forever and each one has the property of unpredictability of the next digit if you know the current digit.</span>

4 0

3 years ago

2(x-1)=3(x-4) how many solutions

34kurt

Distribute
2(x-1) =3(x-4)
2x -2 =3 (x-4)
Distribute
2x-2 =3 (x-4)
2x-2=3x-12
Add 2 both sides of the equation
2x-2=3x-12
2x-2+2=3x-12+2
Simplify
2x=3x-10
Subtract 3x from both sides of the equation
2x=3x -10
2x -3x =3x -10 -3x
Simplify
-x=-10
Divide both sides of the equation by the same term
-x=-10
-x/-1 / -1 / -10/-1
Simplify
X=10
Answer : x=10

6 0

3 years ago

Read 2 more answers

what is the order from least to greatest - 4 with the exponent of 3, square root of 40, square root of 13, square root of 7, , 1

LuckyWell [14K]

Answer: $-4^{3}$ , 14/9 , $\sqrt{7}$ , $\sqrt{13}$ , $\sqrt{40}$

Step-by-step explanation:

$-4^{3}$ = - 64

$\sqrt{40}$ = 6.32455532

$\sqrt{13}$ = 3.605551275

$\sqrt{7}$ = 2.645751311

14/9 = 1.555555556

Arranging from least to greatest , we have :

$-4^{3}$ , 14/9 , $\sqrt{7}$ , $\sqrt{13}$ , $\sqrt{40}$

3 0

3 years ago

Answer please will make first answer brainliest

galina1969 [7]

Answer:

The last one: 70/100 = x/80

And 56 free throws.

Explanation:

70% is 70 out of 100. And if the player is free throwing a total of 80 times, then 80 is 100% of the free throws. Both of the values that represent 100% are the denominators in the fractions.

$\frac{70}{100} = \frac{x}{80}$

The equations are equal, and whatever you do to the bottom, you have to do to the top. 100 was multiplied by 4/5 to get 80. So 70 is multiplied by 4/5 to get x.

4/5 * 70 is 56

8 0

3 years ago

Suppose a line segment whose endpoints are T(x 1 ,y 1 ) and U(x 2 ,y 2 ) is reflected over y=x to create T’U’. The coordinates o

Serjik [45]

Answer:

I have no clue and im a junior im so sorry your teach sucks

6 0

3 years ago

Read 2 more answers