Angles & Missing Angle Detective (90°, 180°, Triangles, Vertical)
Angle relationships allow mathematicians to find unknown measures without a protractor. Master the 4 foundational geometric theorems: Complementary (90°), Supplementary (180°), Triangle Sum (180°), and Vertical Opposite Angles.
🧠 Core Mental Strategies & Shortcuts
📐 Complementary Angles Sum to 90°
Right angles form an L-shape (90°). If one angle is 35°, the missing angle x = 90° − 35° = 55°.
📏 Supplementary Straight Line Angles Sum to 180°
A straight line measures 180°. If one angle is 110°, the supplementary angle is x = 180° − 110° = 70°.
🔺 Triangle Angle Sum Theorem (180°)
All 3 interior angles of any triangle always sum to 180°. If two angles are 50° and 60°, x = 180° − (50° + 60°) = 70°.
❓ Frequently Asked Questions
What are vertical angles?
Vertical angles are opposite angles formed by two intersecting straight lines. They are always perfectly equal in measure.
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