1. ## Trig Identity problem

Hi guys,
I am having trouble with my trig identities I think. I used the cofunction identity to solve what is below.

If sin(48˚) is approximately .74. Use this estimate and the trig identities to find the following:

cos(48˚)

I've attached my work. However this is not the correct answer.

2. ## Re: Trig Identity problem

the co-function identity would make finding $\cos(42^\circ)$ simple, however it's little help in finding $\cos(48^\circ)$ ...

try a variation of the Pythagorean identity, $\cos^2{x}+\sin^2{x} = 1$ ...

$\cos{x} = \sqrt{1-\sin^2{x}}$ for $0 \le x \le 90^\circ$

3. ## Re: Trig Identity problem

Originally Posted by samcolette
Hi guys,
I am having trouble with my trig identities I think. I used the cofunction identity to solve what is below.
If sin(48˚) is approximately .74. Use this estimate and the trig identities to find the following:
cos(48˚)
$\cos(48^o)=\sqrt{1-\sin^2(48^o)}$