3D Trigonometry

Trig can look really scary in 3D….but if you keep calm and simplify it by drawing it as 2D shapes you’ll be rewarded with an A*.


Example: ABCDEFGH is a cuboid with dimensions 8cm, 6cm and 5cm. 3d trig example

  • Find AC

To do this sketch the base of the cuboid and draw the line AC.triangle oneNow you can see to find AC you have a simple Pythagoras problem.

AC2 = AB2 + BC2

AC2 = 82 + 62

AC2 = 100

AC = 10 cm

  • Find AG
For this draw triangle ACG.triangle twoSo again you have Pythagoras.

AG2 = AC2 + CG2

AG2 = 102 + 52

AG2 = 125

AG = 11.18cm (2 d.p.)

  • Find angle GAC
Now trigonometry comes into play!triangle threetanθ = 5/10

i.e θ = 26.57° (2 d.p.)