Polygon Angles with x

Part of the Polygons & Quadrilaterals section of Coddy's Geometry journey. Lesson 4 of 59.

An angle can be labelled with a letter, like x°. The angle sum still works, but now it gives an equation. Here the corners are x°, 2x°, 120° and a right angle. A right angle is 90°.

$Quadrilateral with angles x, 2x, 120 degrees and a right angle$

$x+2x+120+90 = 360$

$3x = 150$

$x = 50$

So the corners are 50° and 100°. Check: $50+100+120+90 = 360$ .

Challenge

Quadrilateral ABCD has a right angle at D. Find x.

Then press Check.

Try it yourself

$Use the figure to find x$

Use the figure to find x

All lessons in Polygons & Quadrilaterals

1Polygons

Angles of a Quadrilateral Angles in Any Polygon How Many Sides?Polygon Angles with xRecap: Polygon Angles

4Parallelograms

Parallelograms Neighbouring Angles Opposite Angles Parallelograms with x A Diagonal Inside Recap: Parallelograms

7On Squared Paper

Make a Parallelogram Draw a Tilted Rectangle Draw a Rhombus Draw a Trapezoid and Kite Recap: Squared Paper

10Composite Shapes

Shapes Made of Parts Rectangle and Triangle Area by Subtracting Enough to Find It?Recap: Composite Shapes

2Regular Polygons

Regular Polygons Inside a Regular Polygon Recap: Regular Polygons

5Rectangles, Rhombi, Squares

Rectangles The Diagonal of a Rectangle Rhombus Angles Squares Recap: Special Parallelograms

8Area of Parallelograms

Area of a Rectangle A Side from the Area Slide the Top Area of a Parallelogram Recap: Parallelogram Area

11Polygon Chases

Parallel Sides in a Pentagon Marks, Not Looks Pentagon with x Regular Shapes Together Recap: Polygon Chases