jika sin x = p dengan x tumpul maka cos (x-120 derajat)=...

[tex]\sin x=p \\ \cos x = \sqrt{1-p^2} \\ \\ \cos(x-120) \\ \cos x\cos 120+\sin x\sin 120 \\ \sqrt{1-p^2}(-\frac{1}{2})+p(\frac{1}{2}\sqrt{3}) \\ \frac{1}{2}(p\sqrt{3}-\sqrt{1-p^2})[/tex]