-3х(6х+у)+2(6х+у)=(6х+у)(-3х+2У)
![cos\alpha = \sqrt{1-sin^{2} \alpha } =\sqrt{1-(-0,8)^{2} } =0,6](https://tex.z-dn.net/?f=cos%5Calpha+%3D+%5Csqrt%7B1-sin%5E%7B2%7D+%5Calpha+%7D+%3D%5Csqrt%7B1-%28-0%2C8%29%5E%7B2%7D+%7D+%3D0%2C6)
в точке
синус равен 0, косинус равен -1
Cos2a=2cos²a-1
2cos2a=2(2*(0,7)²-1)=2(0,98-1)=2*(-0,02)=-0,04
1a) Sin(-45°) * tgП/3 + Cos(- 45°) * ctgП/6 = - 1/√2 * √3 + 1/√2 * √3 =
= - √3/√2 + √3/√2 = 0
б) (Cos540° - Sin840°) / (ctg5П/2 - tg(-9П/4)) = (Cos180° - Sin120°)/ (ctgП/2 +
+ tgП/4) = (- 1 - √3/2)/(0 + 1) = - (1 + √3/2)
2) (tg²a - Sin²a) * ( 1/Sin²a - 1) = tg²a * 1/Sin²a - tg²a - Sin²a * 1/Sin²a =
= 1/Cos²a - tg²a - 1 = (1 - Sin²a - Cos²a)/ Cos²a = [1 - (Sin²a + Cos²a)]/Cos²a=
= 0/Cos²a = 0