Jika sin x=p, maka cos (180°-x)=……

Sinx = p/1
cosx = (1-p^2)^1/2
sin180 = 0
cos180 = -1

cos(180-x) = cos180cosx + sin180sinx
cos(180-x) = (-1)(1-p^2)^1/2
cos(180-x) = – ( 1 – p^2 )^1/2

Sin x=p,

maka,
cos (180°-x) = + sin x
= p
*karena kuadran II