SME
Grade 7 Math · Problem type
Complementary angles
Use this for “Two angles make a right angle. One is 35°. What is the other?”
Diagram
a + b = 90°
35° + 55° = 90°
Complementary angles: together they make a right angle.
This is an example. Type your own values to start a new problem.
a
°
+
b
°
=
90°
Formulas
a
+
b
=
90
(first
angle
+
second
angle
=
90)
35 + 55 = 90
Assumptions
•
The two angles share a ray and together make a right angle.
•
Angles that add to 90° are complementary.
Step-by-step
WE KNOW
a = 35° (first angle)
FIND
second angle (b)
Step 1 · Find second angle (b)
Use a + b = 90 (first angle + second angle = 90)
The two angles make a right angle. Take the other angle away from 90°.
35
+
b
=
90
b
=
90
−
35
b
=
55°
Check
Put the numbers back in. Both sides should match.
35 + 55 = 90 ✓
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Supplementary, complementary, vertical and adjacent angles
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Vertical angles
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