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標題:
A.Maths 小問題
發問:
Prove sinA+sinB+sin(A+B)= 4cos (A over 2)cos (B over2)sin((a+b)over 2)
最佳解答:
L.H.S. = sin A + sin B + sin ( A + B ) = 2 sin [(A+B)/2] cos [(A-B)/2] + 2 sin [(A+B)/2] cos [(A+B)/2] = 2 sin [(A+B)/2] {cos [(A-B)/2] + cos [(A+B)/2] } = 2 sin [(A+B)/2] {2 cos (A/2) cos (B/2)} = 4 cos (A/2) cos (B/2) sin [(A+B)/2] = R.H.S.
其他解答:
A.Maths 小問題
發問:
Prove sinA+sinB+sin(A+B)= 4cos (A over 2)cos (B over2)sin((a+b)over 2)
最佳解答:
L.H.S. = sin A + sin B + sin ( A + B ) = 2 sin [(A+B)/2] cos [(A-B)/2] + 2 sin [(A+B)/2] cos [(A+B)/2] = 2 sin [(A+B)/2] {cos [(A-B)/2] + cos [(A+B)/2] } = 2 sin [(A+B)/2] {2 cos (A/2) cos (B/2)} = 4 cos (A/2) cos (B/2) sin [(A+B)/2] = R.H.S.
其他解答:
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