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Your First Angle

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

Geometry is the mathematics of shapes: lines, angles, triangles, circles. In this journey every lesson shows you a figure, and the canvas beside it holds the mathematics the figure is quietly stating. Your job is to read the picture and work the equation.

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

Here two angles sit on a straight line: 130° and the unknown x°. A straight line always carries 180° in total, so x must be 50. The canvas already says it: x = 50. This time there is nothing to work out. Later, there will be.

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