# Use the Pythagorean identity

Given the sine (or cosine) of an angle, find its cosine (or sine) using the Pythagorean identity.
You might need: Calculator

### Problem

The angle theta, start subscript, 1, end subscript is located in Quadrant I, and cosine, left parenthesis, theta, start subscript, 1, end subscript, right parenthesis, equals, start fraction, 10, divided by, 17, end fraction .
What is the value of sine, left parenthesis, theta, start subscript, 1, end subscript, right parenthesis?