1. The sum of all the internal Angles in a triangle is:
Angles in Triangles
The sum of all the internal
Angles in a triangle is:
How can we find the value of the other
2 angles in the triangle?
180º = the sum of angle 1 + angle 2 + angle 3
180º = 90º + angle 2 + angle 3
Are angle 2 and angle 3 the same or different?
Since angle 1 is 90º, angle 2 and angle 3 must
combine to give us 90º because the internal
angles of a triangle add up to 180º!!
Therefore, angle 2 and angle 3 are both half of 90º 2
180º 1 3
How much is this angle?

2. What kind of triangle is this?
What is the total sum of all the internal
angles of this triangle?
How could you find the value of each
Internal angle?
180º = 3a 3
60º = a
Therefore, all internal angles for this triangle are 60º!
180º = angle1 + angle2 + angle 3
180º = ___ + ___ + ___
If all three angles are the same, then
couldn’t we create an expression to help
us solve the problem?
Let a represent the internal angles
180º = a + a + a