Question

Find cos (2 theta angle) if sin (theta angle) =4/5

Answer 1

Hint: $$ \cos 2 \theta = 1-2 \sin^2 \theta$$

Answer 2

can you do the rest ?

Answer 3

nah im aboslutely clueless about this question

Answer 4

Hm. but I gave you the first clue .. it's just the matter of substitution now..

Answer 5

Anyways the answer is $$ -\frac{7}{25}$$

Answer 6

how you arrive there

Answer 7

$$1-2\times (16/25)$$

Answer 8

16 and 25, 1 and 2...where did all those numbers come from

Answer 9

$$\cos 2 \theta = 1-2 \sin^2 \theta = 1-2\times (\frac 45)^2 = 1-2\times (16/25) = -\frac{7}{25}$$

anything else mam ?

Answer 10

is the cos 2theta= 1-2sin^2theta a rule

Answer 11

yes it's an identity.

Answer 12

ok thanks for the help