Adjacent Angles Practice Problems and Worksheets | Step-by-Step

Master adjacent angles with guided practice problems. Learn to identify, calculate, and solve adjacent angle relationships in parallel lines and intersecting lines.

📚What You'll Master in Adjacent Angles Practice
  • Identify adjacent angles formed when two straight lines intersect
  • Apply the supplementary property: adjacent angles always sum to 180°
  • Distinguish between adjacent, corresponding, alternate, and opposite angles
  • Solve for unknown angles using adjacent angle relationships
  • Work with adjacent angles in parallel lines and transversal problems
  • Calculate missing angles in triangles using adjacent angle properties

Understanding Adjacent angles

Complete explanation with examples

What does adjacent angle mean?

Adjacent angles are the pair of angles formed when two lines intersect each other. These angles are formed at the point where the intersection occurs, and are adjacent to eachother - hence its name. Another pair of angles that are formed at the intersection of two straight lines are the opposite angles, but this pair of angles are opposite at the vertex and not adjacent, so we should not confuse them with adjacent angles. Adjacent angles are always supplementary, that is, together they equal 180° 180° .

The following illustration shows two examples of what adjacent angles look like. One example is red and the other blue.

Adjacent angles new

Detailed explanation

Practice Adjacent angles

Test your knowledge with 48 quizzes

Does the diagram show an adjacent angle?

Examples with solutions for Adjacent angles

Step-by-step solutions included
Exercise #1

If one of two corresponding angles is a right angle, then the other angle will also be a right angle.

Step-by-Step Solution

To solve this problem, consider the following explanation:

When dealing with the concept of corresponding angles, we are typically considering two parallel lines cut by a transversal. The property of corresponding angles states that if two lines are parallel, then any pair of corresponding angles created where a transversal crosses these lines are equal.

Given the problem: If one of the corresponding angles is a right angle, we need to explore if this necessitates that the other corresponding angle is also a right angle.

Let’s proceed with the steps to solve the problem:

  • Step 1: Recognize that we are discussing corresponding angles formed by a transversal cutting through two parallel lines.
  • Step 2: Apply the property that corresponding angles are equal when lines are parallel. This means if one angle in such a pair is a right angle, then the other must be equal to it.
  • Step 3: Since a right angle measures 9090^\circ, the other corresponding angle must also measure 9090^\circ since they are equal by the property of corresponding angles.

Therefore, based on the equality of corresponding angles when lines are parallel, if one corresponding angle is a right angle, the other angle will also be a right angle.

The final conclusion for the problem is that the statement is True.

Answer:

True

Video Solution
Exercise #2

It is possible for two adjacent angles to be right angles.

Step-by-Step Solution

To determine if it is possible for two adjacent angles to be right angles, we start by considering the definition of adjacent angles. Adjacent angles share a common side and a common vertex. We must think about this scenario in terms of the angles lying on a straight line or a flat plane.

A right angle is exactly 9090^\circ. Hence, if we have two right angles that are adjacent, their measures would be:

  • First angle: 9090^\circ
  • Second angle: 9090^\circ

When these two angles are adjacent, as defined in the problem, their sum is:

90+90=180 90^\circ + 90^\circ = 180^\circ

Angles that are adjacent along a straight line add up exactly to 180180^\circ. Therefore, it is indeed possible for two adjacent angles to be both 9090^\circ. This configuration simply means that these two angles lie along a straight line, dividing it into two right angles.

Hence, the statement is True.

Answer:

True

Video Solution
Exercise #3

The sum of adjacent angles is 180 degrees.

Step-by-Step Solution

To solve this problem, let's first understand the concept of adjacent angles. Adjacent angles share a common vertex and a common side. When two adjacent angles are formed by two intersecting lines, they often form what is known as a linear pair.

According to the Linear Pair Postulate, if two angles form a linear pair, then the sum of these adjacent angles is 180180 degrees. This is because these angles lie on a straight line, effectively forming a straight angle, which measures 180180 degrees.

Let's apply this knowledge to the statement in the problem:
The statement says, "The sum of adjacent angles is 180 degrees." In the context of the Linear Pair Postulate, this is indeed correct as adjacent angles that create a linear pair sum to 180180 degrees.

Therefore, when the statement refers specifically to linear pairs, it is true.

Thus, the solution to the problem is True.

Answer:

True

Video Solution
Exercise #4

If one vertically opposite angle is acute, then the other will be obtuse.

Step-by-Step Solution

To solve this problem, we need to understand the properties of vertically opposite angles:

  • Vertically opposite angles are the angles that are opposite each other when two lines intersect.
  • One key property of vertically opposite angles is that they are always equal in measure.
  • An acute angle is defined as an angle that is less than 9090^\circ.
  • An obtuse angle is defined as an angle that is greater than 9090^\circ.

Given that vertically opposite angles are equal, if one angle is acute, the opposite angle must also be acute. This contradicts the statement in the problem that if one is acute, the other will be obtuse.

Therefore, the correct analysis of the problem reveals that the statement is incorrect.

Thus, the solution to the problem is False.

Answer:

False

Video Solution
Exercise #5

Does the drawing show an adjacent angle?

Step-by-Step Solution

Adjacent angles are angles whose sum together is 180 degrees.

In the attached drawing, it is evident that there is no angle of 180 degrees, and no pair of angles can create such a situation.

Therefore, in the drawing there are no adjacent angles.

Answer:

Not true

Video Solution

Frequently Asked Questions

What are adjacent angles and how do I identify them?

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Adjacent angles are pairs of angles formed when two straight lines intersect at a point. They share a common vertex and are next to each other (adjacent). The key property is that adjacent angles are always supplementary, meaning they add up to exactly 180°.

How do I solve adjacent angle problems step by step?

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Follow these steps: 1) Identify the adjacent angle pair at the intersection point, 2) Set up the equation knowing they sum to 180°, 3) Substitute known angle measures, 4) Solve for the unknown angle by subtracting the known angle from 180°.

What's the difference between adjacent angles and corresponding angles?

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Adjacent angles form at the same intersection point and are supplementary (sum to 180°). Corresponding angles occur when parallel lines are cut by a transversal, are in matching positions, and are equal to each other, not supplementary.

Can two obtuse angles be adjacent to each other?

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No, two obtuse angles cannot be adjacent. Since obtuse angles are greater than 90°, two of them would sum to more than 180°. Adjacent angles must be supplementary (sum to exactly 180°), so at least one must be acute.

How do adjacent angles help solve triangle problems?

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Adjacent angles are useful when triangle sides are extended to show exterior angles. The exterior angle and its corresponding interior angle are adjacent and supplementary. This relationship helps find missing interior angles when combined with the triangle angle sum property (180°).

What are the most common mistakes with adjacent angles?

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Common errors include: confusing adjacent with opposite angles (which are equal, not supplementary), forgetting that adjacent angles must sum to 180°, and misidentifying angle pairs in parallel line diagrams. Always check that angles share a vertex and are next to each other.

How do I work with adjacent angles in parallel line problems?

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In parallel line problems, first identify if you're dealing with adjacent angles (at intersection points) or other angle relationships like corresponding or alternate angles. Adjacent angles will always be supplementary regardless of whether the lines are parallel.

What formulas do I need for adjacent angle calculations?

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The main formula is: Adjacent Angle 1 + Adjacent Angle 2 = 180°. If one angle measures x°, then its adjacent angle measures (180 - x)°. This supplementary relationship is the foundation for all adjacent angle problems.

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