Question

Найдите значение выражения 5sin 13pi/12*cos 13pi/12

Answer 1

$5Sinfrac{13pi} {12}*Cos frac{13pi} {12}=5Sin( pi+ frac{pi} {12})*Cos( pi+ frac{pi} {12})=5*(-Sin frac{pi} {12})*(-Cos frac{pi} {12})=2,5*2Sin frac{pi} {12}Cos frac{pi} {12} =2,5Sinfrac{pi} {6}=2,5* frac{1}{2}=1,25$