Verified Answer :

padawan

sin(pi + a) = -sin(a)
sin(4pi/3) = sin(pi + pi/3) = -sin(pi/3)

cos(pi-a) = -cos(a)
cos(5pi/6) = cos(pi -pi/6) = -cos(pi/6)

HomertheGenius
Asin ( 4π/3 ) = sin 240° = sin ( 180° + 60°) = - sin 60° = \(- \frac{ \sqrt{3} }{2}\)

b) cos (5π/6 ) = cos 150° = cos ( 90° + 60° ) = - sin 60°=\(- \frac{ \sqrt{3} }{2}\)

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