Question

AB = 6 cm, AC = 12 cm

Calculate the length of CD.
Give your answer to 3 significant figures.
12 cm
55°
6 cm

Answer 1

12.7 cm

Explanation:

We can obtain CB using Pythagoras :

CB = √12² - 6²

CB = √108

CB = 10.39

Using CB,

We can apply trigonometry on triangle BCD to obtain the length of CD

Sin θ = opposite / hypotenus

Sin 55 = CB / CD

Sin 55 = 10.39 / CD

CD = 10.39 / sin 55

CD = 12.68

CD = 12.7 cm