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發問:

1. In△ABC,a=7cm,b= k cm and A=52°.Find the range of the values of k such that a triangle can be constructed with the given information. 2.Find angle BAD 圖片參考：http://imgcld.yimg.com/8/n/HA00510450/o/701104070090813873422810.jpg

最佳解答:

1)a / sinA = b / sinB7 / sin52° = k / sinBk = sinB (7 / sin52°)Since 0° < B < 180 - 52 = 128° ,the maximum value of sinB = sin90° = 1 the minimum value of sinB = sin0° = 0 Sosin0° (7 / sin52°) < k < sin90° (7 / sin52°)0 < k < 7 / sin52° 2)Let BD = DC = x ,AC / BC = tan 25°AC / (2x) = tan 25° .....(1)AC / DC = tanㄥADC AC / x = tan(ㄥBAD + 25°) ......(2)(2) / (1) :2 = tan(ㄥBAD + 25°) / tan 25°2 tan 25° = tan(ㄥBAD + 25°) 0.93262 = tan(ㄥBAD + 25°) ㄥBAD + 25° = 43°ㄥBAD = 18° 2011-04-07 20:29:06 補充： 1) 0 < k ≤ 7 / sin52°

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