SME
Grade 7 Math · Geometry
Supplementary, complementary, vertical and adjacent angles
Use this for “Two angles are supplementary. One is 115°. What is the other?”
Diagram
a + b = 180°
115° + 65° = 180°
Supplementary angles: together they make a straight line.
This is an example. Type your own values to start a new problem.
a
°
+
b
°
=
180°
Formulas
a
+
b
=
180
(first
angle
+
second
angle
=
180)
115 + 65 = 180
Assumptions
•
The two angles share a vertex and a ray; their outer rays make a straight line.
•
Angles that add to 180° are supplementary.
•
Adjacent angles share a vertex and a ray and do not overlap.
Step-by-step
WE KNOW
a = 115° (first angle)
FIND
second angle (b)
Step 1 · Find second angle (b)
Use a + b = 180 (first angle + second angle = 180)
The two angles make a straight line. Take the other angle away from 180°.
115
+
b
=
180
b
=
180
−
115
b
=
65°
Check
Put the numbers back in. Both sides should match.
115 + 65 = 180 ✓
Topic check
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