Question

if tan theta=20/21 then find the value of cos theta-sin theta/cos theta+sin theta.

Answer 1

20/21=x(let) then by using 20x and 21x by Pythagoras theoram we will get 29x than by substituting the value in the equation
21x/29x-20x/29x/21x/29x+20x/29x
All x will be cut and by subtracting the first and addition of the second we may get 1/29/41/29 so 29 will be cut and the answer we will get 1/41


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Answer 2

Hey,
Here is Your Answer,
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Tan∅=20/21
Tan∅=P/B

Perpendicular = 20 
Base = 21

Find the Hypotenuse 
 P² + B² = H²
(20)² + (21)² = H²
400 + 441 = H²
√841 = H
H = 29

Now Find cos∅ and sin∅
cos∅=B/H                                 sin∅=P/H
cos∅=21/29                              sin∅=20/29
. 
Now Find
      Cos∅-Sin∅/Cos∅+Sin∅
       21/29-20/29             21-20/29            1/29
      ------------------   =      ------------- =       ------- 
       21/29+20/29            21+20/29          41/29

        1        29         1
      -----  x ----- =   -----
      29        41       41
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(I HOPE IT HELPS YOU)
MARK AS A BRILLIANT