NCERT Class XI Mathematics - Trigonometric Functions - Solutions

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Question : 11
Total: 61
sec x =
13
5
, x lies in fourth quadrant.
Solution:  
sec x =
13
5
gives cos x =
5
13

tan2x = sec2 x - 1 ⇒ tan2x =
169
25
- 1 =
144
25
⇒ tan x = ±
12
5

⇒ tan x =
−12
5
⇒ cot x = −
5
12
[since x lies in fourth quadrant]
sin x = tan x × cos x
⇒ sin x =
−12
5
×
5
13
=
−12
13
⇒ cosec x =
−13
12

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