答:sin2xcos3x≠sin5x-sinx。
根据公式sinacosb=1/2(sin(a+b)+sin(a-b))得
sin2xcos3x=1/2(sin(2x+3x)+sin(2x-3x))
=1/2(sin5x+sin(-x))
=1/2(sin5x-sinx)
也可见下图:
sin2xcos3x等于sin5x-sinx
①sin2xcos3x
=1/2(2sin2xcos3x)
=1/2(sin2xcos3x+sin2xcos3x
+cos2xsin3x-cos2xsin3x)
=1/2[(sin2xcos3x+cos2xsin3x)-(cos2xsin3x-sin2xcos3x)
=1/2(sin5x-sinx)
②sin2xcos3x
=1/2(2sin2xcos3x)
=1/2(sin2xcos3x+sin2xcos3x
+cos2xsin3x-cos2xsin3x)
=1/2[(sin2xcos3x+cos2xsin3x)-(cos2xsin3x-sin2xcos3x)]
=1/2(sin5x-sinx)