If cosine, A, equals, start fraction, 28, divided by, 53, end fractioncosA= 53 28 ​ and tangent, B, equals, start fraction, 9, divided by, 40, end fractiontanB= 40 9 ​ and angles A and B are in Quadrant I, find the value of tangent, left bracket, A, minus, B, right brackettan(A−B).