標題:

^o^"懂"就是聰明Maths (2)

發問:

Solve these 2 equations for 0
最佳解答:

1) 2cotx = tanx + 1 2cosx / sinx = sinx / cosx + 1 2 / tanx = tanx + 1 Mutiply by tanx, 2 = tan2x + tanx tan2x + tanx - 2 = 0 (tanx + 2)(tanx - 1) = 0 tanx = -2 or tanx = 1 x = -63.4 or 117 or 45 or 225 So, the solutions are -63.4, 45, 117, 225 2) cosx + secx = 2 cosx + 1 / cosx = 2 Mutiply by cosx cos2x + 1 = 2cosx cos2x - 2cosx + 1 = 0 (cosx - 1)2 = 0 cosx = 1 x = 0, 360 So, the solutions are 0 and 360. 2010-09-19 20:17:29 補充： ok....... 1) 2cotx = tanx + 1 2 / tanx = tanx + 1 2 = tan2x + tanx tan2x + tanx - 2 = 0 (tanx + 2)(tanx - 1) = 0 tanx = -2 or tanx = 1 x = 45, 225, 116.6, 251.6

其他解答:

the ans for the first one is wrong it should be 45, 225, 116.6 , 251.6

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