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If sec A + tan A = 3, then cos A is equal to:
Question

If sec A + tan A = 3, then cos A is equal to:

A.

4/3

B.

3/5

C.

3/4

D.

. 5/3

Correct option is B

Given: 
​sec⁡A+tan⁡A=3\sec A+\tan A =3  
Formula Used: ​
​sec⁡2A=1+tan⁡2Asec⁡2A−tan⁡2A=1(sec⁡A−tan⁡A)(sec⁡A+tan⁡A)=1\sec^2A= 1 + \tan^2 A \\ \sec^2A-\tan^2A =1 \\ (\sec A-\tan A)(\sec A+\tan A) = 1  
​sec⁡A=1cos⁡A\sec A = \frac{1}{\cos A} ​
Solution:
​

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