函數(shù)y=sinx^2+3sinxcosx+5cosx^2的值域是_________
熱心網(wǎng)友
y=sinx^2+3sinxcosx+5cosx^2=sinx^2+cosx^2+3sinxcosx+4cosx^2=1+1.5sin2x+2(cos2x+1)=3+1.5sin2x+2cos2x=3+2.5(sin2x+β)y∈[0.5,5.5]
熱心網(wǎng)友
sinx^2+cosx^2+3sinxcosx+4cosx^2=1+1.5sin2x+2(cos2x+1)這步是怎么算出來的??? 就是用降冪公式 sinx^2=（1-cos2x)/2 cosx^2=(1+cos2x)/2 sinxcosx=(sin2x)/2
熱心網(wǎng)友
對