To prove an identity manually or to follow a calculator's logic, use these standard strategies: 1. Start with the "Messy" Side
A reliable "last resort" is to rewrite every term using only . For example: 4. Apply Algebraic Techniques
If your expression contains two or more fractions, find a common denominator and combine them into a single fraction. This often reveals a Pythagorean identity in the numerator. 3. Convert to Sine and Cosine