Q23 of 118 Page 5

Mark the correct alternative in the following:

If sec x + tan x = k, cos x =


We know tan2x + 1 = sec2x…(1)


Let tan x be a and sec x be b


According to question


a + b =k


Manipulating and Substituting in 1 we get


⇒ a2 – b2 = -1


⇒ (a-b)( a + b) = -1


⇒ (a-b).k =-1


⇒ a-b = -k-1


a + b =k


a-b = -k-1


subtracting above equations we get


2b =k +k-1




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