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Your First Angle

Part of the Angles section of Coddy's Geometry journey. Lesson 1 of 62.

Geometry studies shapes, including lines, angles, triangles, and circles. In this journey, use each diagram's labels and marks to identify an angle relationship. Express that relationship as an equation and solve it on the canvas.

$Two angles on a straight line, 130 degrees and x degrees$

The two adjacent angles form a straight angle, so their measures add to 180°. One is 130°, leaving 180 - 130 = 50 degrees for x. The canvas shows the solved equation x = 50.

Challenge

Easy

The claim on the canvas is already complete: x is 50.

$Two angles on a straight line, 130 degrees and x degrees$

Press Check to confirm it.

Try it yourself

x = 50

Solve for x

All lessons in Angles

1Meet the Angle

Your First AngleNaming Angles Adding Adjacent Angles Degrees and the Full Turn Acute, Right, Obtuse Recap: Adjacent Angles

4Vertical Angles

Linear Pairs Vertical Angles Are Equal Solving with Verticals All Four Angles Recap: At the Crossing

7Crossing Parallel Lines

Parallel Lines Corresponding Angles Alternate Angles Co-interior Angles Which Rule Is It Recap: The Three Pairs

10Isosceles Triangles

Base Angles Are Equal Finding the Apex Which Angles Match Equilateral Angles Isosceles at Work Recap: Twin Corners

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 Expressions Bisecting a Straight Angle Recap: 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