# Area of a Circle (take 2) At the beginning of the term, we saw one approach to computing the area of a circle. Here is another way to view this problem. Consider the circle of radius 1 centered at the

Area of a Circle (take 2)

At the beginning of the term, we saw one approach to computing the area of a circle. Here is another way to view this problem.

Consider the circle of radius 1 centered at the origin. We can represent the curve of the top half of this circle with the function .

1. Integrals in x

Let F(x) represent the shaded area under the curve between t=0 and t=x.

Use geometry to evaluate F(0) and F(1).

Sketch an approximate graph of y = F(x).

Write an integral that represents the shaded area for arbitrary x. (We can’t compute this integral, yet.)

2. Geometry in

Alternatively, we can represent this region in terms of . Let represent the area shaded in the figure below.

Use geometry to evaluate and . (Hint: recall that the area of a sector of a circle with radius r

subtended by an angle a is .)

Sketch an approximate graph of . What is the domain?

Use geometry to write an expression in for , the area of the shaded region for an arbitrary .

Compute the derivative .

3. Integrals in

The figure below shows the relationship between x and .

Use this figure to describe x in terms of . That is, write a formula that computes x given . (Hint: use trigonometry).Substitute this expression for x into the integral for F(x) you wrote in part 1. You now have a function described by an

integral.Use the Fundamental Theorem of Calculus to compute .

Use algebra and trigonometric identities to show that .Use this result to make a conclusion about what must be true about the function .