Two right-angle triangles △ABC and △BCD, have side BC in common, the hypotenuse of △ABC is side AB and the hypotenuse of △BCD is BC.
Given that AB = 18cm, CD = 6cm, and ∠A = 23°, determine the measure of θ = ∠BCD to the nearest degree.
sin 23 = BC / 18
so
BC = 7.033 cm
cos theta = 6/BC = 6 / 7.033 = 0.853
so
theta = cos^-1 (0.853) = 31 degrees