Fundamentals of Math - old

Fundamentals of Mathematics

We also note when triangles contain two or more equal angles, isosceles and equiangular, respectively.

Isosceles Triangle

Equiangular Triangle

Triangles are also classified based on the measurements of their side lengths. In a scalene triangle, none of the side lengths are congruent (same size). In an isosceles triangle, two sides of the triangle are congruent, and equilateral triangles have three congruent sides.

Scalene Triangle

Isosceles Triangle

Equilateral Triangle

Example 5.1

Find the measure of angle PQR and then label the triangle as acute, right, or obtuse.

Recall that the sum of the interior angles of a triangle is 180° . Therefore, the measurement of vertex P, R, and Q must sum to 180° and so it follows:

∠ + ∠ + ∠ = 180°

⟹ 120° + 38° + ∠ = 180°

⟹ 158° − 158° + ∠ = 180° − 158°

⟹ ∠ = 22°

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