Trigonify

Half Angle

sin θ/2

sin⁡θ2=±1−cos⁡θ2\sin\tfrac{\theta}{2} = \pm\sqrt{\dfrac{1 - \cos\theta}{2}}

Related Half Angle identities

cos θ/2tan θ/2

Study this and 44 more identities in the Trigonify workspace — an interactive unit circle, a step-by-step triangle solver, quizzes, and a practice problem bank.