Question

AB = 6 cm, AC = 12 cm

Calculate the length of CD.
Give your answer to 3 significant figures.
C
12 cm
55°
А
D
B 6 cm​

Answer 1

12.7 cm

Explanation:

Pythagoras theorem

c²=a²+b²

12²=6²+b²

144=36+b²

minus 36 on both sides

108=b²

then square root on both sides

b=10.4

wait I'm not done

then we use the sin rule which is

sinx=O

--

H

so

sin(55)=10.4 over H

cross multiply

10.4 over sin 55 which equals 12.7