Consider an acute angle in a right–angled triangle.

MATHEMATICS · Multi-part · CBSE · Mathematics · Introduction to Trigonometry · Introduction to Trigonometry

Problem

Consider an acute angle θ\theta in a right–angled triangle. (i) Define sin⁡θ\sin\theta and cos⁡θ\cos\theta in terms of the sides of the triangle. (ii) Using these definitions, explain why sin⁡(90∘−θ)=cos⁡θ\sin(90^\circ-\theta)=\cos\theta. (iii) State the corresponding identity for cos⁡(90∘−θ)\cos(90^\circ-\theta)."

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