How to Define Product-to-Sum and Sum-to-Product Formulas
TL;DR: Got a product of two trig functions you don’t know what to do with, like sine of A times cosine of B? Product-to-sum formulas rewrite it as a sum or difference of trig functions that’s much easier to handle. Sum-to-product formulas go the other direction. Why bother? Because both transformations turn ugly trig integrals, […]
How to Define Sine, Cosine, and Tangent
TL;DR: Sine, cosine, and tangent are the three ratios that unlock every right triangle. For any acute angle theta inside a right triangle, sine is the opposite side over the hypotenuse, cosine is the adjacent side over the hypotenuse, and tangent is the opposite side over the adjacent side. The mnemonic SOH-CAH-TOA packs all three […]
