Question

Lines AB and CD intersect at point O.
If ∠AOC + ∠BOE = 100° , find ∠COE.

Answer 1

AB is a straight line, so sum of all the angles at 'O' above the line is 180°.

i.e. ∠AOC + ∠COE + ∠EOB = 180${}^{\circ }$$\left[1mark\right]$

or, ∠COE = 180${}^{\circ }$ - (∠AOC + ∠BOE)

Given: ∠AOC + ∠BOE = 100°

Then, ∠COE = 180${}^{\circ }$ - 100°

or, ∠COE = 80${}^{\circ }$$\left[1mark\right]$