## Getting in Shape: Exploring Two-Dimensional Figures

Through a series of hands-on investigations, students first explore some properties of angles and triangles, including the Triangle Inequality Theorem. Next, students analyze properties of regular polygons and develop formulas for area and sums of interior and exterior angles. They then explore circles and develop circumference and area formulas.

### NCTM Standard: Geometry

• Analyze characteristics and properties of two- and three-dimensional geometric shapes and develop mathematical arguments about geometric relationships
• Specify locations and describe spatial relationships using coordinate geometry and other representational systems
• Apply transformations and use symmetry to analyze mathematical situations
• Use visualization, spatial reasoning, and geometric modeling to solve problems

### NCTM Standard: Measurement

• Understand measurable attributes of objects and the units, systems, and processes of measurement
• Apply appropriate techniques, tools, and formulas to determine measurements

### Primary Mathematical Goals

• Use a protractor, ruler, and compass to draw and measure angles, triangles, and polygons
• Understand relationships among the sides and angles of triangles, quadrilaterals, and other polygons
• Create tessellations and other geometric designs
• Explore the relationship between the diameter and the circumference of a circle
• Develop and apply area formulas for regular polygons and circles