4-6 Isosceles Triangles
Before We Begin…
• Mr. A was wrong. The A-Team van was a GMC model, part of General Motors, of which Chevrolet is a subsidiary.
Isosceles Triangle Theorem: if two sides of a triangle are congruent, then the angles opposite of those sides are congruent.
The opposite is true, too!
A triangle is equilateral if and only if it is equiangular
Since all angles=180°,
then every angle in an equilateral triangle is 60°
• That’s It.
• Just use these ideas to find Scooby Doo Clues.
4-7 Triangles and Coordinate Proofs
Don’t worry, this is different!
∆ABC is isosceles
Name the missing coordinates.
• Draw and label an isosceles triangle with base that is a units long, and b units tall.
If you don’t know the value, or cannot find it, just use a new letter.
Draw an isosceles triangle with a base that is 2a long.
Name the missing coordinates
A coordinate proof involves drawing a picture on a graph, and using the distance formula, midpoint formula, and algebra to prove things.
HINT: When drawinga coordinate proof, always use the ORIGIN as a midpoint or vertex !
because (0,0) is easy to work with in the distance formula!
• Let’s try some together!