13(sin^2 53°-cos^2 53°)/cos106°

Question

13(sin^2 53°-cos^2 53°)/cos106°

Answer 1

Sin² 53 = sin² 106\2
cos² 53 = cos² 106\2 =1-sin² 106\2

13*(sin² 106\2 -(1-sin² 106\2 )\cos106 = 13*(sin² 106\2 - 1 + sin² 106\2)\cos106 = 13*(2*sin² 106\2-1)\cos106 = 13*2((1-cos106)\2-1)\cos106 = 13*(1-cos 106-1)\cos106 = 13*(-cos 106)\cos106 = -13

Ответ: -13