There are 4 classifications of triangles by angles. You are probably familiar with them, but glance at the following applets if you need a reminder.
As you drag point B, notice the angles of the triangle. How would you define an acute triangle?
An acute triangle is a triangle whose angles all measure less than 90 degrees.
What do you notice about the angles in the triangle? Using those observations, how would you define an obtuse triangle?
Obtuse triangles have one angle that is greater than 90 degrees.
For this triangle, you can drag the slider to enlarge the triangle or the blue dot to change the shape.
What stayed the same no matter how you changed the triangle? How would you define a right triangle?
A right triangle is a triangle with one 90 degree angle.
Drag the blue point on the triangle until you have two angles that both measure 45 degrees. This triangle has a special name: isosceles right triangle. What could you say about the lengths of two sides of an isosceles right triangle?
The two legs (sides) are congruent.
Use the slider to adjust the size of the triangle.
How would you define an equiangular triangle?
An equiangular triangle is a triangle whose angles always measure 60 degrees. [br][br]
What is another name for this type of triangle (think back to your previous exploration).