**Warmup**

**Activity #1**

** How to Draw a Circle.**

Spend some time familiarizing yourself with the tools that are available in this applet.

- Then draw and label Circle A, with a diameter of 6 cm.

- Draw and label Circle B, with a radius of 5 cm.

- Draw and label Circle C, with a radius that is equal to Circle A’s diameter.

- Draw and label Circle D, with a diameter that is equal to Circle B’s radius.

- Use the compass app below to recreate one of these designs.

**Activity #2**

** Draw Radius and Diameter of a Circle.**

- Use the geometric tool in the applet below to draw a circle.
- Draw and measure a radius and a diameter of the circle.

**Activity #3**

** Name the Radius and Diameter of a Circle.**

Here is a circle with center H and some line segments and curves joining points on the circle.

- Study all the lines that are drawn inside the circle and answer the questions that follow.

(1.) Write down examples of a diameter to the circle. Explain your reasoning.

(2.) Write down examples of a radius to the circle. Explain your reasoning.

**Challenge #1**

Sort these pictures into two groups.

Explain why you sorted the objects like you did.

**Challenge #2**

On January 3rd, Earth is 147,500,000 kilometers away from the Sun. On July 4th, Earth is 152,500,000 kilometers away from the Sun. The Sun has a radius of about 865,000 kilometers.

Could Earth’s orbit be a circle with some point in the Sun as its center? Explain your reasoning.

**Challenge #3**

Lin measured the diameter of a circle in two different directions. Measuring vertically, she got 3.5 cm, and measuring horizontally, she got 3.6 cm. Explain some possible reasons why these measurements differ.

**Quiz Time**

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