Question

prove that sin10pi/3 cos13pi/6 + cos8pi/3 sin5pi/6 = -1​

Answer 1

=> Sin 600° . Cos 390° + Cos 480° Sin 30°

=> - Sin 60° . Cos 30° - Sin 30° Sin 30°

=> - root3/2 . root 3/2 - 1/2 . 1/2

=> -3 - 1/ 4

=> -4/4 = -1

Answer 2

$= > \sin(600) . \cos(390) + \cos(480) \sin(30)$

$= > \sin(60) . \cos(30) - \sin(30) \sin(30)$

$= > \sqrt{ - \frac{3}{2} } . \sqrt{ \frac{3}{2} } - \frac{1}{2}. \frac{1}{2}$

$= > - 3 - \frac{1}{4}$

$= > \frac{ - 4}{4} = - 1$