Question

The diagram shows triangle FGH, with FG = 14cm, GH = 12cm and FH=6cm

i) Calculate the size of angle HFG

Answer 1

58.4°

Explanation:

You have ∆FGH with f = 12 cm, g = 6 cm, and h = 14 cm, and you want to know the measure of angle F.

Law of cosines

The law of cosines tells you ...

f² = g² +h² -2gh·cos(F)

Solving for angle F gives ...

F = arccos((g² +h² -f²)/(2gh))

F = arccos(88/168) ≈ 58.412°

Angle HFG is about 58.4°.