How do you prove -sin( pi/3) = cos ((5pi)/6)sin(π3)=cos(5π6)?

1 Answer
Apr 4, 2016

-sin(pi/3) = sin (pi+pi/3)= cos (pi/2-(pi+pi/3))=cos(-5pi/6)=cos(5pi/6)sin(π3)=sin(π+π3)=cos(π2(π+π3))=cos(5π6)=cos(5π6)

Explanation:

-sinx=sin (pi-x)==cos(pi/2-(pi-x))=cos(-(x+pi/2))=cos(x+pi/2)sinx=sin(πx)==cos(π2(πx))=cos((x+π2))=cos(x+π2)
Here, x=pi/3x=π3.