Question

高中数学计算

cos(a-pi/2)/sin(5pi/2加a)×sin(a-2pi)×cos(2pi-a)

Answer 1

cos(a-pi/2)/sin(5pi/2加a)×sin(a-2pi)×cos(2pi-a)

=cos(π/2 - a)/sin(π/2 +a) ×sina×cos(-a)
=sina/cosa ×sina×cosa
=sin平方a

Answer 2

原式=sina(-cosa)tana(-cosa)sina(-sina)
=-sin²acos²a(sina/cosa)
=-sin^4 acosa