Angle Difference Formula

How to use formula to express exact values

The angle difference identities take two different formulas

sin(A − B) = sinAcosB − cosAsinB
cos(A − B) = cosAcosB + sinAsinB

double angle formula | angle sum formula | pythagorean identities

These formulas allow you to express the exact value of trigonometric expressions that you could not otherwise express. Consider the cos(15°). Unlike the cos(60°) which can be expressed as ½, the cos(15°) cannot simply be represented as a rational expression. However, the angle difference formula allows you to reprsent the exact value of this function Picture of angle difference formula

fraction games onlinemathgames.comlaw of sinesambiguous case of the law of sines