Trigonometric Identities

Hi Friends,

In this post we are sharing some c which are useful for SSC, Railways and other exams.

Pythagorean Identities:

·         sin² ɸ + cos² ɸ = 1

·         1 + tan² ɸ = sec² ɸ

·         1 + cot² ɸ = cosec² ɸ

Reciprocal Identities:

·         sin ɸ = 1/cosec ɸ

·         cos ɸ = 1/sec ɸ

·         tan ɸ = 1/cot ɸ

Ratio Identities:

·         tan ɸ = sin ɸ/cos ɸ

·         cot ɸ = cos ɸ/sin ɸ

Even/Odd Identities:

·         sin (-ɸ) = – sin ɸ                     cosec (-ɸ) = – cosec ɸ

·         cos (-ɸ) = cos ɸ                       sec (-ɸ) = sec ɸ

·         tan (-ɸ) = – tan ɸ                    cot (-ɸ) = – cot ɸ

Cofunction Identities:

·         sin (90-ɸ) = cos ɸ                   cos (90-ɸ) = sin ɸ

·         tan (90-ɸ) = cot ɸ                   cot (90-ɸ) = tan ɸ

·         sec (90-ɸ) = cosec ɸ               cosec (90-ɸ) = sec ɸ

·         sin (90+ɸ) = cos ɸ                   cos (90+ɸ) = – sin ɸ

·         tan (90+ɸ) = – cot ɸ                cot (90+ɸ) = – tan ɸ

·         sec (90+ɸ) = – cosec ɸ             cosec (90+ɸ) = sec ɸ