Trigonometric identities are statements about the relationships of trigonometric ratios. These include reciprocal ratios, complementary angles and the rules for the angle of any magnitude.
Several relationships are shown below:
Reciprocal Ratio & Angles of Any Magnitude:
1. Simplify .
2. Simplify where is an acute angle.
4. Prove .
5. Prove that .
6. Find the exact value of .
8. Simplify .
And more examples of Double Angle and Half Angle problems:
courtesy of shelovesmath.com