Question

Simplify [2 (cos 210 + i sin 210)]^2

Answer 1

2{(cos^210+isin^210)}^2

2(cos^210-sin^10+2i*cos10*sin10)

2(cos20+i*sin20)

cos^2Ф-sin^2Ф=cos2Ф and 2sinФcosФ=sin2Ф here Ф=10°