The angle sum of a triangle equal to 180° .
Triangles are a three sided figure.
A triangle where all three sides equal 60° is called an equilateral.
A triangle which has two of its sides equal in length is called an isosceles triangle.
A triangle with three different sides is called a scalene triangle.
Congruent sides
Two sides of a triangle are congruent if the angle's opposite sides are equal.
- If angle B = angle C, sides opposite equal
- Then AB = AB, angles are equal
Congruent triangles can be determined by ..
SSS - three sides.
SAS - two sides and the contained angle.
ASA - two angles and the contained side.
* If two angles of one triangle are equal to two angles of another triangle, then the third angles of each triangle will be equal.
* If two sides of a right triangle are equal to two corresponding sides of another right triangle, then the third side of each triangle will be equal.
* Once SSS, SAS or ASA is established, the remaining corresponding angles/sides are congruent. This result is called "Corresponding Parts of Congruent Triangles are Congruent" (CPCTC)
Similar Figures
Two figures are similar if ..
1) Corresponding angles are equal.
2) Corresponding sides are in proportion.
AB BC AC
--- = --- = ---
DE EC DC
Corresponding sides of similar figures are in proportion.
