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Simple trigo (Posted on 2014-01-03) Difficulty: 2 of 5
Find the value of

(i)cos 36
(ii)tan 15

using geometry.

No Solution Yet Submitted by Danish Ahmed Khan    
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Solution trying to post thru notepad | Comment 4 of 6 |
tan15
1.       Draw a rectangle ABCD  s.t   AB=CD=1  ;AD=BC=2. 
 
2.       On the side CB mark a point  E  s.t.  AD=AE= 2 . 


3.       Now CE=2- sqrt(3)       angle BAC=60


4.        So angle CDE=15 (since angle AED=
           (150O- 30o)/2=75). 


5.       Since tan 15 =CE/CD        tan 15  =(2- sqrt(3))/1.  
 
6.       finally  tan 15 = 2- sqrt(3) 



7.       The above equals      approximately   .268
1st part later (time allowing)
Ady Tzidon

Edited on January 5, 2014, 12:39 pm
  Posted by Ady TZIDON on 2014-01-04 18:06:04

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