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Example of angles formed by lines intersect
Question:
In the figure below, lines l1 // l2. Lines l3, l4 and l1 intesect at point O. If the angle 3 = 120o and angle 1 = 80o, what is the degree measure of angle 2?
find the angles when several lines intersect
Solution:
since l3 and l4 intersect at point O (Given)
so angle 1 = angle AOB (vertical angles are equal)
since l1 // l2 (Given)
so angle 3 = angle AOC (alternate interior angles are equal)
angle AOC = angle AOB + angle BOC
angle 3 = angle 1 + angle 2
so angle 2 = angle 3 - angle 1
= 120o - 80o
= 40o
therefore, the degree measure of the angle 2 is 40o