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Bisecting a Straight Angle

Part of the Angles section of Coddy's Geometry journey. Lesson 29 of 62.

Bisect the biggest angle on a line: the straight angle itself. Half of 180° is 90°, so the bisector of a straight angle stands at a perfect right angle to the line. Bisecting a straight angle builds perpendicularity.

$A straight angle bisected into two right angles of 90 degrees$

A straight angle measures 180°. Bisecting it divides that measure by 2, producing two 90° angles. The bisector is therefore perpendicular to the original line.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Angles

2Straight Lines and Supplements

Angles on a Line Supplementary Angles Three Angles on a Line Write the Equation Recap: Along the Line

5Around a Point

Angles Around a Point The Missing Angle Equal Slices Four Angles, One Point Recap: The Full Turn

8Transversal Problems

Both Angles Labeled Verticals Meet Parallels From Figure to Equation Alternate with Algebra Recap: Through the Strip

11The Exterior Angle

The Exterior Angle Using the Shortcut Two Roads, One Answer Exterior in the Wild Recap: Outside View

3Right Angles and Complements

Complementary Angles Finding the Complement Perpendicular Lines Equal Parts of a Corner Recap: The Right Corner

6The Angle Bisector

The Angle Bisector Bisected ExpressionsBisecting a Straight AngleRecap: Split in Half

9Triangle Angle Sum

The 180 Rule Finding the Third Angle Two Unknown Angles Right Triangles Recap: The Budget

12Final Challenges

Final: The Angle Chase Final: Triangle Meets Line Final: The Full Round Final: Isosceles Chase Final: Master of Angles