1. lesson 20.notebook September 25, 2012
Lesson 20:
*Naming Triangles...
By angles:
• 3 acute angles>acute triangle
• 1 right angle>right triangle
• 1 obtuse angle>obtuse triangle
By sides:
• 3 equal sides>equilateral triangle
• at least 2 equal sides>isosceles triangle
• no equal sides>scalene triangle
1
2. lesson 20.notebook September 25, 2012
Formula for area of a triangle:
*base height or 1/2(base height)
2
(Base and height must
be perpendicular!!)
*The SUM of the measures
of the angles in a triangle
= 180 degrees
2
3. lesson 20.notebook September 25, 2012
Examples Lesson 20
pg. 129
A) isosceles triangle & right triangle
B) equilateral triangle & acute triangle
C) obtuse triangle & scalene triangle
D) x =
y =
3
