Trigonometric Identities

Hello Readers,

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

Values of some Trigonometric Functions:

Click here to read: How to find Minimum and Maximum values of Trigonometric Functions