1. Warm-up

2. Homework WS 8.4
Practice 8.4 Link

3. Lesson 8.5 Areas of Circles
Learning Intentions
I will derive Review the formula for the area of a circle
2) I will apply area formulas to solve problems
Success Criteria
I will successfully complete 80% of my practice problems

4. So far…
We have seen that the parallelograms area could be transformed to derive the areas of other shapes.

6. A = πr²

7. Animation of Investigation
The following is an animation of the previous investigation in case you couldn’t get it!
Remember that the circumference of a circle is C = 2πr.
You can use the circumference of a circle to find its area by dividing the circle and rearranging the pieces to form a parallelogram.

8. Example
The small apple pie has a diameter of 7 in, and the large cherry pie has a radius of 6 in. How much larger is the large pie?
Small Pie
Large Pie
– = in2
The large pie is in2 larger than the small pie.

9. Example 2 Find the area of the inscribed circle.
Find the area of circle P in terms of
A = pr2
A = p(8)2 P
A = 64p cm2
16 cm
Find the area of the inscribed circle.
Find the area of the shaded region.

10. Now do some practice!