Question

найдите ctg альфа если cos альфа 5/13

Answer 1

$ctg alpha = frac{cos alpha }{sin alpha } \ sin alpha = sqrt{1- cos^{2} alpha } = sqrt{1- frac{25}{169} } = sqrt{ frac{144}{169} } = frac{12}{13} \ ctg alpha = frac{5}{12}$

Answer 2

cosα=⁵/₁₃
sinα=√1-cos²α=√1-(⁵/₁₃)²=√1-²⁵/₁₆₉=√¹⁴⁴/₁₆₉=¹²/₁₃
ctgα=cosα / sinα=⁵/₁₃ : ¹²/₁₃=⁵/₁₂