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Rhombus Angles

Part of the Polygons & Quadrilaterals section of Coddy's Geometry journey. Lesson 24 of 61.

A rhombus is a quadrilateral with four equal sides. Its opposite sides are parallel (the chevrons say so), so it is a parallelogram, and everything about parallelogram angles holds. The equal sides add something more.

$Rhombus ABCD with the diagonal AC and a 120 degree angle at B$

The diagonal AC cuts the rhombus into triangles ABC and ACD, and in each one two sides are sides of the rhombus. So both triangles are isosceles. With ∠B = 120°, the base angles of triangle ABC are (180 - 120) / 2 = 30 degrees each: ∠BAC = ∠BCA = 30°. Pick Isosceles triangle for them.

Challenge

ABCD is a rhombus with ∠ABC = 110°, and the diagonal AC is drawn. Find ∠BAC, marked ?, then press Check.

Try it yourself

$Find the marked part of the figure$

Find the marked part of the figure

Test yourself

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

All lessons in Polygons & Quadrilaterals

2Regular Polygons

Regular Polygons From an Angle to the Sides Inside a Regular Polygon Recap: Regular Polygons

5Rectangles, Rhombi, Squares

Rectangles The Diagonal of a RectangleRhombus AnglesSquares 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