F.4 Maths Question

2010-05-12 7:51 pm
Applications of Trigonometry in 2-dimensional Problems

1. In the figure, BCD is a straight line. AB = 11 cm, AC = 10cm , AD = 14cm and CD = 7cm .

(a) Find ∠ACD
(b) Find ∠ABC

回答 (2)

2010-05-12 11:13 pm
✔ 最佳答案
a) In △ ACD , by cosine formula ,

cos ㄥACD = (10^2 + 7^2 - 14^2) / (2*10*7)

ㄥACD = 109.61598°

b)

In △ABC , by sine formula ,

(sin ㄥABC) / 10 = (sin ㄥACB) / 11

(sin ㄥABC) / 10 = [sin (180 - 109.61598)°] / 11

sin ㄥABC = 0.85633

ㄥABC = 58.9°

2010-05-12 7:54 pm
figure??????????


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