Find the measure of the angle
We have hundreds of course questions with personalized recommendations + Account 100% premium
Find the measure of the angle
Remember that the sum of angles in a triangle is equal to 180 degrees.
Therefore, we will use the following formula:
Now let's input the known data:
We'll move the term to the other side and keep the appropriate sign:
45
Can a triangle have a right angle?
This is a fundamental property of triangles in flat (Euclidean) geometry. No matter the size or shape of the triangle, the three interior angles will always sum to exactly 180 degrees!
Look for angle markings like the curved lines in the diagram. The numbers 80° and 55° are clearly labeled, so you have everything needed to find the third angle!
No! All angles in a triangle must be positive and less than 180°. If you get a negative answer, check your arithmetic - you likely made an error.
Use the format: . Substitute known values: , then solve for the unknown angle.
Double-check your addition and subtraction. Common errors include: 80 + 55 = 135, then 180 - 135 = 45. Make sure each step is correct!
Get unlimited access to all 18 Angles questions, detailed video solutions, and personalized progress tracking.
Unlimited Video Solutions
Step-by-step explanations for every problem
Progress Analytics
Track your mastery across all topics
Ad-Free Learning
Focus on math without distractions
No credit card required • Cancel anytime