Acute Triangle Practice Problems - Types of Triangles

Master acute triangles with step-by-step practice problems. Learn to identify and classify triangles by angles using the Pythagorean theorem and angle measurements.

📚What You'll Master in These Acute Triangle Practice Problems
  • Identify acute triangles by checking if all angles are less than 90°
  • Use the Pythagorean theorem to classify triangles as acute, obtuse, or right
  • Apply angle sum properties to determine if three angles can form a triangle
  • Compare side lengths to determine triangle type using mathematical inequalities
  • Solve real-world problems involving acute triangle identification and classification
  • Distinguish between acute, obtuse, and right triangles using multiple methods

Understanding Acute triangle

Complete explanation with examples

Definition of Acute Triangle

An acute triangle has all acute angles, meaning each of its three angles measures less than 90° 90° degrees and the sum of all three together equals 180° 180° degrees. 

Detailed explanation

Practice Acute triangle

Test your knowledge with 20 quizzes

Is the triangle in the drawing an acute-angled triangle?

Examples with solutions for Acute triangle

Step-by-step solutions included
Exercise #1

Is the triangle in the drawing a right triangle?

Step-by-Step Solution

Due to the presence of the 90 degree angle symbol we can determine that this is indeed a right-angled triangle.

Answer:

Yes

Exercise #2

In a right triangle, the two sides that form a right angle are called...?

Step-by-Step Solution

In a right triangle, there are specific terms for the sides. The two sides that form the right angle are referred to as the legs of the triangle. To differentiate, the side opposite the right angle is called the hypotenuse, which is distinct due to being the longest side. Hence, in response to the problem, the sides forming the right angle are correctly identified as Legs.

Answer:

Legs

Exercise #3

In a right triangle, the side opposite the right angle is called....?

Step-by-Step Solution

The problem requires us to identify the side of a right triangle that is opposite to its right angle.
In right triangles, one of the most crucial elements to recognize is the presence of a right angle (90 degrees).
The side that is directly across or opposite the right angle is known as the hypotenuse. It is also the longest side of a right triangle.
Therefore, when asked for the side opposite the right angle in a right triangle, the correct term is the hypotenuse.

Selection from the given choices corroborates our analysis:

  • Choice 1: Leg - In the context of right triangles, the "legs" are the two sides that form the right angle, not the side opposite to it.
  • Choice 2: Hypotenuse - This is the correct identification for the side opposite the right angle.

Therefore, the correct answer is Hypotenuse \text{Hypotenuse} .

Answer:

Hypotenuse

Exercise #4

Fill in the blanks:

In an isosceles triangle, the angle between two ___ is called the "___ angle".

Step-by-Step Solution

In order to solve this problem, we need to understand the basic properties of an isosceles triangle.

An isosceles triangle has two sides that are equal in length, often referred to as the "legs" of the triangle. The angle formed between these two equal sides, which are sometimes referred to as the "sides", is called the "vertex angle" or sometimes more colloquially as the "main angle".

When considering the vocabulary of the given multiple-choice answers, choice 2: sides,mainsides, main accurately fills the blanks, as the angle formed between the two equal sides can indeed be referred to as the "main angle".

Therefore, the correct answer to the problem is: sides,mainsides, main.

Answer:

sides, main

Exercise #5

In an isosceles triangle, the angle between ? and ? is the "base angle".

Step-by-Step Solution

An isosceles triangle is one that has at least two sides of equal length. The angles opposite these two sides are known as the "base angles."
The side that is not equal to the other two is referred to as the "base" of the triangle. Thus, the "base angles" are the angles between each of the sides that are equal in length and the base.
Therefore, when we specify the angle in terms of its location or position, it is the angle between a "side" and the "base." This leads to the conclusion that the angle between the side and the base is the "base angle."

Therefore, the correct choice is Side, base.

Answer:

Side, base.

Frequently Asked Questions

What makes a triangle an acute triangle?

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An acute triangle has all three angles measuring less than 90 degrees. The sum of all angles still equals 180°, but each individual angle is acute (less than 90°).

How do you identify an acute triangle using side lengths?

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Use the Pythagorean theorem: if a² + b² > c² (where c is the longest side), then the triangle is acute. If the sum of squares of the two shorter sides is greater than the square of the longest side, all angles are acute.

Can a triangle have angles of 70°, 60°, and 50°?

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Yes, this forms an acute triangle. All three angles are less than 90°, and they sum to 180° (70° + 60° + 50° = 180°), satisfying both requirements for a valid acute triangle.

What's the difference between acute, obtuse, and right triangles?

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• Acute triangle: All angles < 90° • Right triangle: One angle = 90° • Obtuse triangle: One angle > 90° The angle sum is always 180° for all triangles.

How do you solve triangle classification problems step by step?

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1. Identify the longest side (potential hypotenuse) 2. Apply the Pythagorean theorem: compare a² + b² to c² 3. If a² + b² > c², it's acute; if equal, it's right; if less, it's obtuse

Why can't angles of 90°, 115°, and 35° form a triangle?

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These angles sum to 240°, which exceeds the required 180° for any triangle. The fundamental rule is that interior angles of any triangle must always sum to exactly 180°.

What are common mistakes when identifying acute triangles?

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Students often forget to check ALL angles are less than 90°, or incorrectly apply the Pythagorean theorem by not identifying the longest side first. Always verify the angle sum equals 180°.

Can an equilateral triangle be an acute triangle?

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Yes, an equilateral triangle is always acute because each angle measures exactly 60°, which is less than 90°. It's the most common example of an acute triangle.

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