All Intermediate Geometry Resources
Example Question #1 : How To Find The Length Of The Diagonal Of A Pentagon
In the pentagon below, the length of is one-third that of . Find the length of diagonal .
Start by using the Pythagorean theorem to find the length of .
Since is one-third the length of , we know that the length of must be .
Now, notice that the pentagon is made up of one rectangle and two right triangles.
Focus on rectangle . We can find the length of by adding together the lengths of and .
Since we are working with a rectangle, we know that . Thus, we can use the Pythagorean Theorem again to find the length of .
Make sure to round to two places after the decimal.
Example Question #2 : How To Find The Length Of The Diagonal Of A Pentagon
What is the length of a diagonal of a pentagon with side length of 20 centimeters (to the nearest tenth)?
Let be the length fo a diagonal.
One interior angle of a pentagon measures
A diagonal of this pentagon, along with two sides, forms an isosceles triangle with sides 20, 20 and ; the side of length is opposite the angle of measure , and each side of length 20 is opposite an angle of measure .
The Law of Sines helps us to determine :