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 #11 : How To Find If Right Triangles Are Congruent
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 & B
B & C
All three.
A & C
None of these
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.