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

Does the diagram show an obtuse triangle?

Examples with solutions for Acute triangle

Step-by-step solutions included
Exercise #1

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 #2

In an isosceles triangle, what are each of the two equal sides called ?

Step-by-Step Solution

In an isosceles triangle, there are three sides: two sides of equal length and one distinct side. Our task is to identify what the equal sides are called.

To address this, let's review the basic properties of an isosceles triangle:

  • An isosceles triangle is defined as a triangle with at least two sides of equal length.
  • The side that is different in length from the other two is usually called the "base" of the triangle.
  • The two equal sides of an isosceles triangle are referred to as the "legs."

Therefore, each of the two equal sides in an isosceles triangle is called a "leg."

In our problem, we confirm that the correct terminology for these two equal sides is indeed "legs," distinguishing them from the "base," which is the unequal side. This aligns with both the typical definitions and properties of an isosceles triangle.

Thus, the equal sides in an isosceles triangle are known as legs.

Answer:

Legs

Exercise #3

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 #4

Does the diagram show an obtuse triangle?

Step-by-Step Solution

To determine if the triangle in the diagram is obtuse, we will visually assess the angles:

  • Step 1: Identify the angles in the diagram. The triangle has three angles, with one angle appearing between the horizontal base and the left slanted side.
  • Step 2: Evaluate the angle between the base and the left side. If it opens wider than a right angle, it's considered obtuse. This angle seems to be greater than 9090^\circ, indicating obtuseness.
  • Step 3: Conclude based on visual inspection. Since this key angle is greater than 9090^\circ, the triangle must be an obtuse triangle.

Therefore, the solution to the problem is Yes; the diagram does show an obtuse triangle.

Answer:

Yes

Video Solution
Exercise #5

Does the diagram show an obtuse triangle?

Step-by-Step Solution

To determine if the triangle shown in the diagram is obtuse, we proceed as follows:

  • Step 1: Identify that the diagram is indeed a triangle by observing the confluence of three edges forming a closed shape.
  • Step 2: Appreciate the geometric arrangement of the triangle, focusing on the sides' lengths and angles visually.
  • Step 3: Noticeably, the longest side of the triangle represents a noticeable tilt indicating the presence of an obtuse angle.

Based on the observation above, notably from the triangle's longest side against the base, it's clear that one angle is larger than 9090^\circ. Hence, the triangle in the diagram is indeed an obtuse triangle.

Therefore, the correct answer is Yes.

Answer:

Yes

Video Solution

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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