A.Maths Trigonometry @ 百科全書

標題:

A.Maths Trigonometry

發問:

Express 9sinΦ - 40cosΦ in the form of rcos(Φ +β)

最佳解答:

9sinΦ - 40cosΦ = √(92 + 402) (9 sin Φ /√(92 + 402) - 40 cos Φ/√(92 + 402)) = 41 (9 sin Φ /41 - 40 cos Φ/41) = 41 (sin 12.7 sin Φ - cos 12.7 cos Φ) = 41 cos (Φ + 12.7) 2008-08-03 22:37:13 補充： Sorry, redo: 9sinΦ- 40cosΦ=41 (9 sin Φ /41 - 40 cos Φ/41) = 41 (sin 167.3 sin Φ + cos 167.3 cos Φ) = 41 cos (Φ - 167.3)

其他解答:

Please refer to the following solution: 圖片參考：http://hk.geocities.com/stevieg_1023/12.gif