Obtuse Triangle Practice Problems & Exercises Online

Master obtuse triangles with interactive practice problems. Learn to identify obtuse angles, calculate missing angles, and solve triangle classification exercises step-by-step.

📚What You'll Master in Obtuse Triangle Practice
  • Identify obtuse triangles by recognizing angles greater than 90 degrees
  • Calculate missing obtuse angles using the 180-degree triangle angle sum
  • Compare angle sizes in obtuse triangles to determine relationships
  • Solve algebraic equations to find unknown obtuse angle measurements
  • Classify triangles as obtuse, acute, or right using the Pythagorean theorem
  • Apply obtuse triangle properties to solve real-world geometry problems

Understanding Obtuse Triangle

Complete explanation with examples

Obtuse Triangle Definition

An obtuse triangle is a triangle that has one obtuse angle (greater than 90° 90° degrees and less than 180° 180° degrees) and two acute angles (each of which is less than 90° 90° degrees). The sum of all three angles together is 180° 180° degrees.

Detailed explanation

Practice Obtuse Triangle

Test your knowledge with 20 quizzes

Does the diagram show an obtuse triangle?

Examples with solutions for Obtuse 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 obtuse?

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An obtuse triangle has one angle greater than 90° but less than 180°, and two acute angles less than 90°. The sum of all three angles always equals 180°, just like any triangle.

How do you find the obtuse angle in a triangle?

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To find an obtuse angle: 1) Add the two known acute angles, 2) Subtract their sum from 180°, 3) The result is your obtuse angle. Remember, the obtuse angle is always the largest angle in the triangle.

Can a triangle have two obtuse angles?

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No, a triangle cannot have two obtuse angles. Since each obtuse angle is greater than 90°, two obtuse angles would sum to more than 180°, which exceeds the total angle sum possible in any triangle.

What's the difference between obtuse and acute triangles?

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Obtuse triangles have one angle greater than 90°, while acute triangles have all three angles less than 90°. Obtuse triangles appear "wider" or more "spread out" compared to the sharper appearance of acute triangles.

How do you use the Pythagorean theorem to identify obtuse triangles?

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For sides a, b, and c (where c is longest): If a² + b² < c², the triangle is obtuse. If a² + b² = c², it's right. If a² + b² > c², it's acute.

What are common mistakes when solving obtuse triangle problems?

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Common errors include: forgetting that only ONE angle can be obtuse, miscalculating the 180° angle sum, confusing obtuse angles (>90°) with reflex angles (>180°), and incorrectly applying the Pythagorean theorem for classification.

Are obtuse triangles used in real life?

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Yes! Obtuse triangles appear in architecture (roof designs), engineering (bridge supports), art (geometric patterns), and navigation (triangulation methods). Understanding their properties helps in construction and design fields.

What formulas do I need for obtuse triangle practice problems?

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Key formulas include: Angle sum (A + B + C = 180°), Pythagorean test (a² + b² vs c²), and basic algebraic manipulation for solving angle relationships like A = 2B or C = ½A.

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