Verifying Identities

A trigonometric identity is an equation or formula involving only trigonometric functions that is valid for all angles measured in degrees or radians or for real numbers for which both sides of the equality are defined. To verify a trigonometric identity we use the fundamental trigonetric identities, the even-odd properties, and the basic arithmetic and algebraic operations. In order to verify a trigonometric identity, we are required to show that the given expressions are equivalent. Some suggestions for verifying identities includes: simplifying the more complicated side of the equation first and finding least common denominators for sums or differences of fractions. Also if the two preceding suggestions fail, then express all trigonometric functions in terms of sines and cosines and try to simplify. In the end, don't treat a trigonometric equation as an identity until after you have proven that it is really true.