Trigonometric Formulas (High School Level) Leave a Comment / By Team Sheetdigest / 12 September 2023 Pythagorean Identities \sin^2(\theta) + \cos^2(\theta) = 1 \tan^2(\theta) + 1 = \sec^2(\theta) \cot^2(\theta) + 1 = \csc^2(\theta) Reciprocal Identities \sec(\theta) = \frac{1}{\cos(\theta)} \csc(\theta) = \frac{1}{\sin(\theta)} \cot(\theta) = \frac{1}{\tan(\theta)} Quotient Identities \tan(\theta) = \frac{\sin(\theta)}{\cos(\theta)} \cot(\theta) = \frac{\cos(\theta)}{\sin(\theta)} Co-function Identities (Complimentary angles) \sin\left(\frac{\pi}{2} - \theta\right) = \cos(\theta) \cos\left(\frac{\pi}{2} - \theta\right) = \sin(\theta) \tan\left(\frac{\pi}{2} - \theta\right) = \cot(\theta) \sec\left(\frac{\pi}{2} - \theta\right) = \csc(\theta) \csc\left(\frac{\pi}{2} - \theta\right) = \sec(\theta) \cot\left(\frac{\pi}{2} - \theta\right) = \tan(\theta)
