Question

How do you prove `-sin( pi/3) = cos ((5pi)/6)`?

Answer 1

`-sin(pi/3) = sin (pi+pi/3)= cos (pi/2-(pi+pi/3))=cos(-5pi/6)=cos(5pi/6)`

Explanation:

`-sinx=sin (pi-x)==cos(pi/2-(pi-x))=cos(-(x+pi/2))=cos(x+pi/2)`
Here, `x=pi/3`.