perplexus.info :: Geometry : Simple trigo

Simple trigo (Posted on 2014-01-03)

Find the value of

(i)cos 36
(ii)tan 15

using geometry.

No Solution Yet Submitted by Danish Ahmed Khan

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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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