Question

若sina-cos分之sina+cosa等于二分之一则tan2a等于?

Answer 1

由已知(sina +cosa)/(sina – cosa) = 1/2,去分母可得2sina + 2cosa = sina – cosa,移项可得sina = -3cosa,因为cosa ≠ 0,所以tana = -3,进而tan2a =(2tana)/(1 – tan2a) = 2*(-3)/[1 – (-3)2] = -6/(1 – 9) = 3...