Question

正弦和余弦的和差化积公式

Answer 1

sinA+sinB = 2 sin[(A+B)/2] * cos[(A-B)/2]

sinA-sinB = 2 cos[(A+B)/2] * sin[(A-B)/2]

cosA+cosB = 2 cos[(A+B)/2] * cos[(A-B)/2]

cosA-cosB = -2 sin[(A+B)/2] * sin[(A-B)/2]