sinA+sinB
=2sin[(A+B)/2]cos[(A-B)/2]
=2sin75°cos[(A-B)/2]
当A=B=75°时,式子取最大值2sin75°
当A-B=360°k+180°时,式子取最小值-2sin75°
三角函数极值求法SINA+SINBA+B=150求上式的最大值
sinA+sinB
=2sin[(A+B)/2]cos[(A-B)/2]
=2sin75°cos[(A-B)/2]
当A=B=75°时,式子取最大值2sin75°
当A-B=360°k+180°时,式子取最小值-2sin75°