Question

26sin(п/2+α),если sinα = -15/13 и a принадлежит (п; 3п/2)

Answer 1

$26Sin(\frac{\pi }{2}+\alpha)=26Cos\alpha \\\\\alpha\in(\pi;\frac{3\pi }{2})\Rightarrow Cos\alpha<0\\\\26Cos\alpha=-26\sqrt{1-Sin^{2}\alpha} =-26\sqrt{1-(-\frac{5}{13})^{2}}=-26\sqrt{1-\frac{25}{169}}=-26\sqrt\frac{144}{169}=-26*\frac{12}{13}=-24$