化简三角函数式子(level1下 P30)

题目

化简三角函数式子(level1下 P30)
1) sin(α+180度)*cos(-α)*sin(-α-180度) (是否等于 -(sinα)平方*cosα)
2) (sin(-α))立方*cos(2π+α)*tan(-α-π) (是否等于 (sinα)四次方)

答案

11.
sin(α+180度)*cos(-α)*sin(-α-180度)
=[- sinα]*cos(-α)*[-sin(-α)
=[- sinα]*[cos(α)]*[sin(α)]
=-[sinα]^2*[cos(α)]
2.
(sin(-α))立方*cos(2π+α)*tan(-α-π)
=(-sina)^3*cosa*tan(-a)
=-(sina)^3*cosa*(-tana)
=(sina)^3*cosa*sina/cosa
=(sina)^4