JSS1: MATHEMATICS - 3RD TERM
Statistics I | Week 12Topics|1 Quiz
Statistics II | Week 23Topics|1 Quiz
Statistics III | Week 35Topics|1 Quiz
Properties of Plane Shapes | Week 41Topic|1 Quiz
Solid Shapes and their Properties | Week 51Topic|1 Quiz
Angles: Measurement I | Week 62Topics|1 Quiz
Angles: Measurement II | Week 71Topic|1 Quiz
Angles between Lines | Week 85Topics|1 Quiz
Angles in a Triangle | Week 92Topics|1 Quiz
Angles in a Triangle
Tri-angle means three angles.
A triangle is the simplest form of polygon with three sides and three interior angles.
Sum of angles in a triangle is 180º
\( \scriptsize \angle A \: + \: \angle B \: + \: \angle C = 180^o \)
From the above diagram above
a = y (alternate angles)
b = z (alternate angles)
but, a + x + b = 180º (sum of angles on a straight line).
Since a + b = y + z
Hence x + y + z = a + x + b = 180º
Therefore, the sum of angles of a triangle = 180º