F4 Maths sine law ( -_-) zzZ

👨🏻‍🏫 學術台數學

Anonymous

2010-03-03 6:57 am

In the figure, ABCD is a trapezium with AD // BC, AD = 10 cm,
BC = 21 cm, angle ABC = 63 degree and angle DCB = 47 degree. Find AB.

Figure: [img]http://img199.imageshack.us/img199/9164/79436181.jpg[/img]

更新1:

http://img199.imageshack.us/img199/9164/79436181.jpg

回答 (2)

☆柑桔↗

2010-03-03 7:23 am

✔ 最佳答案

add DX, so DX//AB, DX=AB, ADBX is an //gram
XC=21-10cm=11cm

angle dxc=180-63-47=70(angle sum of tri.)

(sin 70)/11 = (sin 47)/dx 9(sin formula)

ab=dx=8.561193884...cm

圖片參考：http://imgcld.yimg.com/8/n/HA00195895/o/701003020179013873415320.jpg

記得補番d degree符號呀-v-"

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老爺子

2010-03-03 7:53 am

Method 1 : Using sine law
http://i320.photobucket.com/albums/nn347/old-master/100302_2a.jpg?t=1267544916

圖片參考：http://i320.photobucket.com/albums/nn347/old-master/100302_2a.jpg?t=1267544916

Method 2 : Using right-angled triangles
http://i320.photobucket.com/albums/nn347/old-master/100302_2b.jpg?t=1267544874

圖片參考：http://i320.photobucket.com/albums/nn347/old-master/100302_2b.jpg?t=1267544874

參考: 老爺子

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