Circle the pairs that are complementary (sum to 90°) and underline the pairs that are supplementary (sum to 180°):
30° + 60° = 90°
Complementary / Supplementary
110° + 70° = 180°
Complementary / Supplementary
Practice Problems:
a) Find the complement of 45°: ______
b) Find the supplement of 120°: ______
c) If two angles are complementary and one is 35°, what is the other? ______
• Complementary angles: Two angles that add up to 90°
• Supplementary angles: Two angles that add up to 180°
• To find complement: 90° - given angle
• To find supplement: 180° - given angle
Complementary Angles: Two angles whose measures sum to 90°
Supplementary Angles: Two angles whose measures sum to 180°
• Look for the C in "Complementary" - it reminds you of 90° (Corner)
• Look for the S in "Supplementary" - it reminds you of 180° (Straight)
• Always check your answers by adding the angles together
Look at the intersecting lines and identify:
Adjacent Angles: ∠1 and ∠2, ∠2 and ∠3, ∠3 and ∠4, ∠4 and ∠1
Vertical Angles: ∠1 and ∠3, ∠2 and ∠4
True or False:
a) ∠1 and ∠2 are vertical angles: ______
b) ∠1 and ∠3 are vertical angles: ______
c) Adjacent angles are always supplementary: ______
• Adjacent angles: Share a common vertex and side, but no interior points
• Vertical angles: Opposite angles formed by intersecting lines, always equal
• Linear pairs: Adjacent angles that form a straight line (always supplementary)
- Look for shared vertices and sides for adjacent angles
- Identify opposite angles for vertical angles
- Check if angles form a straight line for linear pairs
- Calculate sums to verify complementary/supplementary relationships
In the diagram with parallel lines cut by a transversal, identify:
Corresponding Angles: ∠1 and ∠2 are equal
Alternate Interior Angles: ∠3 and ∠4 are equal
Find the measures: If ∠1 = 70°, then ∠2 = ______
If ∠3 = 110°, then ∠4 = ______
• Corresponding angles: Angles in matching positions are equal
• Alternate interior angles: Angles inside the parallel lines on opposite sides of the transversal are equal
• Co-interior angles: Angles inside the parallel lines on the same side of the transversal are supplementary
An angle bisector divides an angle into two equal parts. Solve:
Problem 1: If the original angle is 100°, what is the measure of each part after bisecting? ______
Problem 2: If one part of a bisected angle is 25°, what was the original angle? ______
Problem 3: If ∠1 = 30°, what is the original angle? ______
• An angle bisector divides an angle into two equal parts
• Each part is half the original angle
• Original angle = 2 × (one part)
• Each part = Original angle ÷ 2
Problem 1: In the figure, lines AB and CD are parallel, and EF is a transversal. If ∠AEF = 70°, find all other angles.
Given: ∠AEF = 70°, AB || CD
Step 1: ∠AEF and ∠CFE are corresponding angles → ∠CFE = 70°
Step 2: ∠AEF and ∠BEF form a linear pair → ∠BEF = 180° - 70° = 110°
Step 3: ∠BEF and ∠DFE are corresponding angles → ∠DFE = 110°
Step 4: ∠CFE and ∠DFC form a linear pair → ∠DFC = 110°
Problem 2: Two angles are supplementary. One angle is 3 times the other. Find both angles.
Let x = smaller angle
Then 3x = larger angle
x + 3x = 180° (supplementary)
4x = 180°
x = 45°
So angles are 45° and 135°
• Identify all given information
• Apply relevant angle theorems
• Set up equations based on relationships
• Solve systematically
• Verify your answers
Linear Pair: Adjacent angles that sum to 180°
Vertical Angles: Opposite angles that are equal
Parallel Line Properties: Corresponding, alternate, and co-interior angles
Problem 1: A ladder leans against a wall, forming a 75° angle with the ground. What is the angle between the ladder and the wall?
Answer: ______° (Show your work)
Problem 2: The hands of a clock at 3:00 form what type of angle? At 2:30?
Answer: 3:00: ______ | 2:30: ______
Problem 3: A roof has two slanted sides meeting at a peak. If each slant forms a 40° angle with the horizontal, what angle do the two slants make with each other?
Answer: ______°
• Architecture: Building structures rely on angle measurements
• Engineering: Bridges use specific angle relationships
• Sports: Athletes use angles for optimal performance
• Navigation: Directions are measured in angles
• Multi-step problems: Apply multiple angle relationships in sequence
• Algebraic approach: Use variables to represent unknown angles
• Proof-based thinking: Justify each step with geometric properties
• Real-world applications: Connect angle concepts to practical situations
Get the full set of printable worksheets with answer keys:
- Complementary and Supplementary angles
- Adjacent and Vertical angles
- Parallel lines with transversals
- Angle bisectors and constructions
- Identify all angle relationships confidently
- Solve multi-step angle problems
- Apply theorems in complex situations
- Connect angles to real-world applications