F.4 Maths
2010-03-13 7:17 pm
In △ABC,b:c=3:2,a=14cm and A=60°.Find b and c.(Leave your answers in surd form.)
回答 (1)
2010-03-13 8:15 pm
✔ 最佳答案
Given b:c=3:2, let b = 3k,c=2kby Cos law, a = √(b^2 + c^2 - 2bccosA)
14 = √(3k)^2 + (2k)^2 - 2(3k)(2k)cos60
...
k = 2√7
b= 3k = 3(2√7) = 6√7cm
c= 2k= 2(2√7) = 4√7cm
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