Calculate Parallelogram Area: Circle with Circumference 25.13 and Tangent Points

Question

Below is a circle bounded by a parallelogram:

36

All meeting points are tangential to the circle.
The circumference is 25.13.

What is the area of the parallelogram?

Video Solution

Solution Steps

00:11 Let's find the area of the parallelogram.
00:15 Lines starting from the same point are equal until they meet.
00:24 A side is equal to the sum of its parts.
00:34 Draw a diameter in the circle.
00:39 The radius is always at a right angle to the tangent where they meet.
00:44 We'll use the circle's circumference formula to find the radius.
00:49 Let's substitute the values and find the radius.
00:58 Round this radius. Now we know the radius and diameter!
01:05 To get the area, multiply the height, E H, by the side, A B.
01:11 Substitute the values and solve for the area.
01:14 And that's how we solve this problem.

Step-by-Step Solution

First, we add letters as reference points:

Let's observe points A and B.

We know that two tangent lines to a circle that start from the same point are parallel to each other.

Therefore:

AE=AF=3 AE=AF=3
BG=BF=6 BG=BF=6

And from here we can calculate:

AB=AF+FB=3+6=9 AB=AF+FB=3+6=9

Now we need the height of the parallelogram.

We know that F is tangent to the circle, so the diameter that comes out of point F will also be the height of the parallelogram.

It is also known that the diameter is equal to two radii.

Since the circumference is 25.13.

Circumference formula:2πR 2\pi R
We replace and solve:

2πR=25.13 2\pi R=25.13
πR=12.565 \pi R=12.565
R4 R\approx4

The height of the parallelogram is equal to two radii, that is, 8.

And from here you can calculate with a parallelogram area formula:

AlturaXLado AlturaXLado

9×872 9\times8\approx72

Answer

72 \approx72