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If sin x=-4/5 and x lies in 3^rd quadrant, then find sec x.(a) 5/3(b) 3/5(c) -3/5(d) -5/3I got this question in an interview.This intriguing question comes from Trigonometric Functions topic in chapter Trigonometric Functions of Mathematics – Class 11

Answer»

Right choice is (d) -5/3

The EXPLANATION is: SIN X=-4/5

We know, sin^2x + COS^2x=1

cos^2x = 1-(-4/5)^2 = 1-16/25=9/25

cos x=±3/5

cos x is negative in 3^rd QUADRANT so, cos x=-3/5.

sec x = 1/cos x = 1/(-3/5) = – 5/3.



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