sina*cosb=1/2,则cosa*sinb的取值范围?
问题描述：
sina*cosb=1/2,则cosa*sinb的取值范围?
说明思路.
答
sin(A+B) = sinA*cosB + cosAsinBcosA*sinB = sin(A+B) - sinA*cosB = sin(A+B) - 1/2因为 1≥sin(A+B)≥ -1所以1/2 ≥ cosAsinB ≥ -3/2sin(A-B) = sinA*cosB - cosAsinBcosA*sinB = sinA*cosB - sin(A-B) = 1/2 - ...