Question

Help with trigonometry​

Answer 1

cos ∠CBD = - 4√41 / 41

Explanation:

AB = 4 ΔABC = (4 x AC) / 2 = 10

AC = 5

BC = √5² + 4² = √41

cos ∠CBD = cos (180° - ∠CBA) = cos 180° cos ∠CBA + sin 180° sin ∠CBA

(cos 180° = - 1 sin 180° = 0 cos ∠CBA = 4 / √41 )

cos ∠CBD = (-1) x cos ∠CBA = - 4 / √41 = - 4√41 / 41