sinx的立方是否等于1/4(3sinx+sin3x)我估计是相等的求推倒过程~~~

Question

sinx的立方
是否等于1/4(3sinx+sin3x)
我估计是相等的
求推倒过程~~~

Answer 1

sin(3x)=sin(x+2x)=sin(x)cos(2x)+cos(x)sin(2x)=sin(x)[1-2sin��(x)]+2[1-sin��(x)]sin(x)=3sin(x)-4sin��(x),sin��(x)=(1/4)[3sin(x)+sin(3x)] .