Tan (π + a) = - 1 / 2, the value of sin (A-7 π) cos (a + 5 π) can be obtained

Tan (π + a) = - 1 / 2, the value of sin (A-7 π) cos (a + 5 π) can be obtained

tan(π+a)=-1/2
So Tana = - 1 / 2
sina/cosa=-1/2
-2sina=cosa
So Sina * cosa