Three Relationships, and the Angle Actually Asked

You'll learnto name the angle relationship in a diagram, then report the angle actually asked.

Angles come in three relationships — supplementary to 180°, complementary to 90°, and vertical and equal — triangles carry a 180° sum, and similar triangles scale by matched sides. Watch where the points leak: confusing the relationships, flipping a similarity ratio, and reporting the solved variable instead of the angle that was actually asked.

8 STEPS · 6 QUICK CHECKS · 180, 90, or equal · answer the angle, not x · v3

angles · triangles

Before you start

What you're looking at

A diagram of two angles resting on a straight line, labeled a° and b°, beside a card of three relationships.

The question

Which relationship does this diagram use, and is x the same as the angle asked?

Watch for

Watch the relationship get named first; here two angles on a line sum to 180°.

What the symbols mean

a° and b° are the two unknown angles; the card lists supplementary, complementary, and vertical relationships.

Keep these separate

x is the variable you solve for — the angle the question actually asks for is often a different number.

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