Mathematics

Mathematics

Problem

For an acute angle ϕ\phi, let cot⁡ϕ=k\cot\phi = k where k>0k>0. Express the six trigonometric ratios of ϕ\phi in terms of kk, namely: (i) sin⁡ϕ\sin\phi (ii) cos⁡ϕ\cos\phi (iii) tan⁡ϕ\tan\phi (iv) csc⁡ϕ\csc\phi (v) sec⁡ϕ\sec\phi (vi) cot⁡ϕ\cot\phi.
Intuitive explanation

The key insight is to use the Pythagorean identity to build a right triangle from the given cotangent ratio. Since cot⁡ϕ=k=adjacentopposite\cot\phi = k = \frac{\text{adjacent}}{\text{opposite}}, you can set the opposite side to 1 and adjacent side to kk, then find the hypotenuse using the Pythagorean theorem. Once you have all three sides, all six ratios follow directly from their definitions.

Intuitive explanation

The key insight is to use the Pythagorean identity to build a right triangle from the given cotangent ratio. Since cot⁡ϕ=k=adjacentopposite\cot\phi = k = \frac{\text{adjacent}}{\text{opposite}}, you can set the opposite side to 1 and adjacent side to kk, then find the hypotenuse using the Pythagorean theorem. Once you have all three sides, all six ratios follow directly from their definitions.

Browse the problem library