The ideas in this geometry lesson are taken from the Geometry ebook that I sell at MathMammoth.com. This lesson plan does not contain all the problems the Geometry ebook does.
Equilateral and isosceles triangles
Free geometry lesson plan from HomeschoolMath.net
Example problem types
1. Draw an isosceles triangle (a triangle that has two equal sides). Start out by drawing the two sides that have equal measure and draw the third side last. Use a ruler to make sure they are equal.
2. Make a guess about the angles in an equilateral triangle:
Then measure the angles in the equilateral triangles above. What do you notice?
ALL the angles are _______ degrees.
Based on that fact, draw an equilateral triangle. You can choose the length of the sides.
|An isosceles triangle has two angles that have the same measure.
They are called the base angles, The remaining angle is called the top angle.
4. a) Draw an isosceles triangle whose base angles are 40.
What is the top angle? The length of the sides can be any.
b) Draw an isosceles triangle whose base angles are 75. What is the top angle? Again the length of the sides can be any.
a) Is it possible to have an equilateral right triangle? Why?
If so, draw one.
b) Is it possible to have an equilateral obtuse triangle? Why? If so, draw one.
f) Is it possible to have an isosceles acute triangle? Why? If so, draw one.
7. Calculate the angles. Don't measure, because the pictures are not exact. Note especially if the triangle(s) are equilateral or isosceles.
[Pictures available in the ebook]
New terms to remember: