Finding the Third Angle of a Triangle Given Two Angles
Use the triangle angle sum theorem to calculate the measure of the third angle when two angles are known.

Use the triangle angle sum theorem to calculate the measure of the third angle when two angles are known.
Upgrade to unlock this lesson, practice questions, and your personal tutor.
10th Grade · Math · TEKS
8 lessons
Prove and apply the triangle angle sum theorem, exterior angle theorem, and base angles theorem, and use isosceles triangle properties to solve for unknown angles and sides.
verify theorems about the relationships in triangles, including proof of the Pythagorean Theorem, the sum of interior angles, base angles of isosceles triangles, midsegments, and medians, and apply these relationships to solve problems; and
use a problem-solving model that incorporates analyzing given information, formulating a plan or strategy, determining a solution, justifying the solution, and evaluating the problem-solving process and the reasonableness of the solution;