Double-angle formulas express trigonometric functions of twice an angle in terms of functions of the original angle.
Triple-angle formulas extend the concept of double-angle formulas:
These formulas express squared trigonometric functions in terms of first-degree functions:
Half-angle formulas express trigonometric functions of half an angle in terms of functions of the original angle:
Product-to-sum formulas express the product of sine and cosine functions as a sum or difference.
Sum-to-product formulas express sums of sine and cosine functions as products.