# Q3, W8: February 24-28 Geometry Teacher Kristin Andreason Geometry Honors 8 February 24-28 Unit 6: Two-Dimensional Measurements
Standard(s) Taught

MAFS.912.G-GMD.1.1:  Give an informal argument for the formulas for the circumference of a circle, area of a circle, volume of a cylinder, pyramid, and cone. (Use dissection arguments, Cavalieri’s principle, and informal limit arguments.)

MAFS.912.G-GPE.2.7:  Use coordinates to compute perimeters of polygons and areas of triangles and rectangles, e.g., using the distance formula.

Learning Targets and Learning Criteria
• define regular polygons.
• inscribe a regular polygon in a circle and break it into many congruent triangles to find its area.
• explain and use the dissection method on regular polygons to generate an area formula for regular polygons A = ½ × apothem × perimeter (A = aP).
• calculate the area of a regular polygon A = ½ × apothem × perimeter   (A = ½aP).
• use pictures to explain that a regular polygon with many sides is nearly a circle, its perimeter is nearly the circumference of a circle, and that its apothem is nearly the radius of a circle.
• substitute the “nearly” values of a many sided regular polygon into   A = ½ × apothem × perimeter (A = ½aP) to show that the formula for the area of a circle is A = πr2.
• use the distance formula to compute the perimeter and area given the coordinates of vertices of a polygon like triangle, square, rectangle, kite, rhombus, trapezoid, etc.
• decompose more complex figures whose vertices are given using coordinates into familiar shapes that are easier to work with.
Classroom Activities

Monday/Tuesday:

• Students will do a Square/Rhombus Partner Activity.
• We will do some of IXL N.2 and N.3 together to review.
• We will do a Review on Quadrilaterals with Plickers.
• I will show them on Math Open Reference how to inscribe a square, a hexagon, and an equilateral triangle in a circle.

Wednesday:

• We will create a foldable on Area of 2D figures and I will give them notes on this.

Thursday/Friday:

• I will introduce Area of Regular Polygons
• Students will create a foldable on Area of Regular Polygons
• Students will do part of a scavenger hunt on area of regular polygons
Assignments Due
• Scavenger hunt on Area of Regular Polygons due on February 27/28.