1/4*sin^x+1/2*sin2x
=1/4 sin²x+sinxcosx
=(1/4 sin²x+sinxcosx)/(sin²x+cos²x)
分子分母同除以cos²x
=(1/4tan²x+tanx)/(tan²x+1)
=(1/4+1)/(1+1)
=5/8