Wednesday, 15 July 2015

trigonometry - Find the angle inside a triangle in terms of two variables : alpha,beta




In the adjoining figure(below)



Figure of the problem



CZ is perpendicular to XY and the ratio of AZ to ZB is 1:2. The angle ACX is α and the angle BCY is β. Find an expression for the angle AZC in terms of α and β.



By using the sine rule (in my opinion, which can be used here):



AZsin(90α)=ZCsinACB=ACsinAZC.........(1)




BZsin(90β)=ZCsinABC=BCsin(πAZC)=sinAZC..........(2)



Now AZZB=12(Given)



AZZCZBZC=12........(3)



Using (1),(2) and (3), we get,



ACBC=sinABCsinCAB= 12cosβcosα




Again CAB+ABC=α+β(by careful observation)



Again using cosine rule on ΔACZ, we get



AC2+ZC22ACZCsinα=AZ



Putting value of AZ above in (1), we get,



AC2+ZC22ACZCsinαcosα=ACsinAZC




But here I am stuck as I think I am going somewhere else. Please give me any suggestion, idea or directly, the answer(if you'd actually do that I'll be obliged)



The probable solution is below:



enter image description here


Answer



Your solution looks good to me.


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