
law of tangents


Assume that a, b, c represent the lengths of the three sides of a triangle, and A, B, C represent the angles opposite these three sides. Then the law of tangents states that
(ab)/(a+b) = tan[(1/2)(AB)]/tan[(1/2)(A+B)] (bc)/(b+c) = tan[(1/2)(BC)]/tan[(1/2)(B+C)] (ca)/(c+a) = tan[(1/2)(CA)]/tan[(1/2)(C+A)]

