Question

Вычислите cos(п/6+а), если cosa= -(5/13); п

Answer 1

sina=√1-25/169=√144/169=12/13
cos(π/6+a)=cosπ/6*cosa-sinπ/6sina=√3/2*(-5/13) -1/2*12/13=-(5√3+12)/26