You can identify triangles by their angle measurements. Using the fact that all angles in a triangle add up to 180 degrees, you apply some algebra to determine whether a triangle is equiangular, isosceles, scalene, right, acute, or obtuse.
Practice questions
Triangle WXY is drawn with
![image0.png](https://www.dummies.com/wp-content/uploads/501315.image0.png)
extended to
![image1.png](https://www.dummies.com/wp-content/uploads/501316.image1.png)
Use the diagram and the given information to classify each triangle as acute, obtuse, equiangular, or right.
![image2.png](https://www.dummies.com/wp-content/uploads/501317.image2.png)
-
is 20 more than
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is 30 more than twice
Answers and explanations
Acute
Write down the given angle measures:
The sum of the three angles of a triangle is 180 degrees:
Find the measure of each angle by plugging in 55 degrees for x:
Because the largest angle of this triangle is less than 90 degrees, this triangle is acute.
Right
These two angles form a linear pair, so they add up to 180 degrees. Use these relationships to solve for x and find
Therefore,
With this info and the given
find the measure of the remaining angle in the triangle:
If one angle in the triangle is 90 degrees, then the triangle is a right triangle.