May 18, 2015

Students show that a quadrilateral is cyclic if and only if its opposite angles are supplementary.

Students derive and apply the area of cyclic quadrilateral ABCD as 1/2 AB·CD·sin(w) where w is the measure of the acute angle formed by diagonals AB and CD.

Teacher and Student versions of full lesson from engageNY

- Mathematics > General
- Mathematics > Geometry

- Grade 9
- Grade 10

Reason abstractly and quantitatively.

Use appropriate tools strategically.

Attend to precision.

Look for and make use of structure.

Construct the inscribed and circumscribed circles of a triangle, and prove properties of angles for a quadrilateral inscribed in a circle.