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

Is the triangle in the diagram isosceles?

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

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

Step-by-Step Solution

To determine whether a triangle is acute-angled, we note that all interior angles must be less than 90∘90^\circ. While numerical angle measures are not given, the drawing representation can be analyzed.

Consider the triangle's shape in its entirety. An acute triangle, by definition, implies each angle of the triangle measures less than 90∘90^\circ. Therefore:

  • No angle appears to be 90∘90^\circ or greater based on the shape's symmetry and proportion as drawn.
  • If a right angle existed, it would visually resemble an "L" flip or similar straight form.
  • Acuteness indicates a slender or symmetric appearance without any extended right-angle resemblance.

Based on these observations, the triangular drawing presents no visual evidence of existing right or obtuse angles.

Therefore, the shape corresponds best with an acute-angled triangle's properties. Conclusively, the answer to whether the triangle is acute-angled is Yes.

Answer:

Yes

Video Solution
Exercise #5

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

Step-by-Step Solution

To solve this problem, we need to determine if the triangle depicted is an acute-angled triangle.

An acute-angled triangle is defined as a triangle where all internal angles are less than 90∘90^\circ.

Upon observing the triangle in the drawing, it appears that each of its angles is less than 90∘90^\circ. The shape of the triangle does not present any right angles (90∘90^\circ) or angles greater than 90∘90^\circ.

Thus, based on the visual inspection and understanding of triangle properties, the triangle appears to be acute-angled.

Therefore, the solution to the problem is Yes, the triangle is an acute-angled triangle.

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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