The figure shows the plan of a garden ABCDE. ABC is a straight line and AE per-pendicular AC.The lengths of ED and DC are 38 m and 21 m respectively. angle
AED=65degree, angleABD=135degreeand angle BDC=90degree.
(a) Find the length of AB.
(b) Find the length of AE.
(c) Find the perimeter of the garden ABCDE.
picture:http://postimg.org/image/63th8jkt5/
NEED STEP,PLZ!!!
Trigonometric ratio problem
2013-12-07 10:56 pm
回答 (2)
2013-12-08 4:04 pm
✔ 最佳答案
Angle DBC = 180 - 135 = 45 degree. So BD = DC = 21 ( isos. triangle).Angle BDC = 360 - 90 - 135 - 65 = 70 degree.
By cosine rule,
BE = sqrt [ 38^2 + 21^2 - 2(38)(21)cos70] = 36.5942
By sine rule,
38/sin(angleDBE) = 36.5942/sin(angleBDE)
so angle DBE = arcsin [ 38 sin 70/36.5942] = 77.3672 degree
so angle ABE = 135 - 77.3672 = 57.6328 degree
AB = BE cos 57.6382 = 19.5875
AE = BE sin 57.6382 = 30.9106
BC = sqrt ( 21^2 + 21^2) = 29.6985
So perimeter of garden = 19.5875 + 29.6985 + 21 + 38 + 30.9106 = 139.1966.
2013-12-08 6:25 pm
The answer is wrong!!!(a) is 8.48 and (b) is 30.7.NEED STEP PLZ
收錄日期: 2021-04-25 22:39:47
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20131207000051KK00092