Pythagorean Identities
Jump to navigation
Jump to search
Theorem
Sum of Squares of Sine and Cosine
- $\cos^2 x + \sin^2 x = 1$
Difference of Squares of Secant and Tangent
- $\sec^2 x - \tan^2 x = 1 \quad \text {(when $\cos x \ne 0$)}$
Difference of Squares of Cosecant and Cotangent
- $\csc^2 x - \cot^2 x = 1 \quad \text {(when $\sin x \ne 0$)}$
Source of Name
This entry was named for Pythagoras of Samos.
Sources
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): Pythagorean identities
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): Pythagorean identities