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Note: In a right triangle, one of the angles measures is 90º and each one
of the remaining two angles is acute.
 Angle sum property (IMPORTANT)
The sum of all the angles of a triangle is 180º.
Example1:<A = 50º , <B = 60º and <C =70º. Is it the measures of the triangle?
Solution: <A + <B + <C = 50º + 60º +70º = 180º.
Yes, it can be the measures of the triangle because it follows the angle sum
property.
Example2: One of the two equal angles of an isosceles triangle measures 40º.
Find all the angles of the triangle.
Solution: The sum of two angles of the triangle = 40º +40º = 80º (because two
sides of an isosceles triangle is same)
Sum of the all the angles = 180º
So, the third side = 180º - 80º =100º