GEO-05 · Geometry and Trigonometry

Lines, angles, and polygons

Lines, angles, and triangles · Stage 1

01 · Key idea

Interior angles of a triangle total 180°.

Useful ruletriangle 180°; polygon (n−2)180°

02 · Worked example

Two angles of a triangle are 50° and 60°. Find the third.

This teaching example is original and is not an official SAT question.

Reasoning

180−50−60=70.

Answer

70°

03 · Next step

Practice questions remain in English, as on the SAT.

GEO-05 · Lines, angles, and polygons