All Basic Geometry Resources
Example Questions
Example Question #1481 : Plane Geometry
Are these right triangles congruent?
Cannot be determined - we need at least one pair of angles, or all three sides
No - at least one pair of corresponding sides is not congruent
No - the angles are different
Yes - all three pairs of sides must be congruent by Pythagorean Theorem
Yes - by the angle-angle-side theorem
Yes - all three pairs of sides must be congruent by Pythagorean Theorem
Right now we can't directly compare these triangles because we do not know all three side lengths. However, we can use Pythagorean Theorem to determine both missing sides. The left triangle is missing the hypotenuse:
The right triangle is missing one of the legs:
subtract 2,304 from both sides
This means that the two triangles both have side lengths 48, 55, 73, so they must be congruent.
Example Question #1481 : Basic Geometry
The hypotenuse and acute angle are given for several triangles. Which if any are congruent? Triangle A- Hypotenuse=15; acute angle=56 degrees. Triangle B- Hypotenuse=18; acute angle=56 degrees. Triangle C-Hypotenuse=18; acute angle= 45 degrees.
A & C
All three.
B & C
None of these
A & B
None of these
The correct answer is none of these. There are several pairs of angles and sides or sides and angles that must be the same in order for two triangles to be congruent.
In our case, we need the acute angle and the hypotenuse to both be equal. No two triangles above have this relationship and therefore no two are congruent.
Example Question #1483 : Basic Geometry
Given: and .
and are both right angles.
True or false: From the above information, it follows that .
True
False
True
If we seek to prove that , then , , and correspond to , , and , respectively.
By the Hypotenuse-Leg Theorem (HL), if the hypotenuse and one leg of a triangle are congruent to those of another, the triangles are congruent.
and are both right angles, so and are both right triangles. and are congruent corresponding sides, and moreover, since, each includes the right-angle vertex as an endpoint, they are congruent corresponding legs. and are opposite the right angles, making them congruent corresponding hypotenuses.
The conditions of HL are satisfied, so .
Example Question #302 : Right Triangles
Given: and .
and are both right angles.
True or false: From the given information, it follows that .
False
True
False
The congruence of and cannot be proved from the given information alone. Examine the two triangles below:
, , and and are both right angles, so the conditions of the problem are met; however, since the sides are not congruent between triangles - for example, - the triangles are not congruent either.
Example Question #1 : How To Find The Height Of A Right Triangle
A right triangle has a hypotenuse of 18 inches and a base of 12 inches. What is the height of the triangle in inches?
We can find one leg of a right triangle when we have the length of the hypotenuse and the other leg. Square the hypotenuse and the known leg. Then, subtract the squared length of the leg from the squared length of the hypotenuse. Finally, find the square root of the result.
Example Question #1 : How To Find The Height Of A Right Triangle
If c is not the base of the triangle, which of the following is the height?
None of the other answers
or
or
If is not the base, that makes either or the base. If either or is the base, the right angle is on the bottom, so or respectively will be perpendicular. The height of a triangle is the distance from the base to the highest point, and in a right triangle that will be found by the side adjoining the base at a right angle. So if the base is , then and vise versa.
Example Question #1 : How To Find The Height Of A Right Triangle
The area of a right triangle is 28. If one leg has a length of 7, what is the length of the other leg?
We begin with the formula for the area of a triangle.
We further realize that the two legs of the triangle are the base and height; therefore, substituting what we know we get
We can then solve by simply dividing.
We have found our height and thus the second leg of our triangle.
Example Question #1 : How To Find The Height Of A Right Triangle
If the area of a right triangle is , and the base of the right triangle is , what is the height of the right triangle?
Recall how to find the area of a right triangle:
Now, we are going to manipulate the equation to solve for height.
Now, plug in the information given by the question about the values of the area and base of the triangle to find the height.
Example Question #1 : How To Find The Height Of A Right Triangle
If the area of a right triangle is , and the base of the triangle is , what is the height of the triangle?
Recall how to find the area of a right triangle:
Now, we are going to manipulate the equation to solve for height.
Now, plug in the information given by the question about the values of the area and base of the triangle to find the height.
Example Question #1 : How To Find The Height Of A Right Triangle
If the area of a right triangle is , and the base of the triangle is , what is the height of the triangle?
Recall how to find the area of a right triangle:
Now, we are going to manipulate the equation to solve for height.
Now, plug in the information given by the question about the values of the area and base of the triangle to find the height.