I learned that sin^2(theta) + cos^2(theta) = 1, but for a problem we did, sin^2(15) - cos^2(15) = 1. I don't understand how this works, how do you use the Pythagorean Identity to manipulate the steps into getting 1?

Printable View

- May 14th 2012, 11:18 AMdaigoConfused about Pythagorean Identity
I learned that sin^2(theta) + cos^2(theta) = 1, but for a problem we did, sin^2(15) - cos^2(15) = 1. I don't understand how this works, how do you use the Pythagorean Identity to manipulate the steps into getting 1?

- May 14th 2012, 11:27 AMSylvia104Re: Confused about Pythagorean identity
Use the identity In your example,

- May 14th 2012, 11:29 AMdaigoRe: Confused about Pythagorean Identity
Wait, so then we solved the problem incorrectly? the answer is not equal to 1? Ugh...I wish I knew when a solution was wrong...I spent all afternoon trying to decipher how the arrived was arrived at.

- May 14th 2012, 11:33 AMskeeterRe: Confused about Pythagorean Identity
- May 15th 2012, 11:19 AMHallsofIvyRe: Confused about Pythagorean Identity
Specifically, is NOT !