maths.com >>>> Trigonometry >>>> Identities

Trigonometry - Identities

Pythagorean Identities

 

Sin2θ + Cos2θ = 1

 

Sin2θ + Cos2θ = 1

Divide through by Sin2θ

Sin2θ   Cos2θ   1
+
=
Sin2θ   Sin2θ   Sin2θ

and we get

1 + Cot2θ = Cosec2θ

 

Sin2θ + Cos2θ = 1

Divide through by Cos2&theta

Sin2θ   Cos2θ   1
+
=
Cos2θ   Cos2θ   Cos2θ

and we get

Tan2θ + 1 = Sec2θ

 

 

 

 
maths.com Home


sin2 + cos2 = 1

tan2 + 1 = sec2

1 + cot2 = cosec2

These may be easier to remember as

sin2 + cos2 = 1

sec2 = 1 + tan2

cosec2 = 1 + cot2
Edited by Dr David Cornelius an Independent Private Maths Tutor with over 25 years of experience and The Secretary of The Association of Tutors in the UK for 15 years.
Contact
Disclaimer
Copyright
Privacy
Feedback