Triangle Angle Validation: Do 31°, 122°, and 85° Form a Valid Triangle?

Triangle Angle Sum with Invalid Measures

Tree angles have the sizes:

31°, 122°, and 85.

Is it possible that these angles are in a triangle?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:08 Let's see if these angles can make a triangle.
00:12 Remember, in a triangle, all angles add up to one hundred eighty degrees.
00:16 Plug in the given angles and calculate their sum.
00:20 If the total is more than one hundred eighty degrees, it's not a triangle.
00:26 And that's how we find the solution!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Tree angles have the sizes:

31°, 122°, and 85.

Is it possible that these angles are in a triangle?

2

Step-by-step solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

We'll add the three angles to see if their sum equals 180:

31+122+85=238 31+122+85=238

Therefore, these cannot be the values of angles in any triangle.

3

Final Answer

Impossible.

Key Points to Remember

Essential concepts to master this topic
  • Rule: Sum of all triangle angles must equal exactly 180°
  • Technique: Add given angles: 31° + 122° + 85° = 238°
  • Check: If sum ≠ 180°, angles cannot form triangle ✓

Common Mistakes

Avoid these frequent errors
  • Assuming angles can form a triangle without checking
    Don't skip adding the angles and assume they form a valid triangle = wrong conclusion! Large angles like 122° should signal potential issues. Always calculate the sum first and verify it equals exactly 180°.

Practice Quiz

Test your knowledge with interactive questions

Is DE side in one of the triangles?
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FAQ

Everything you need to know about this question

Why must triangle angles add to exactly 180°?

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This is a fundamental property of triangles in flat geometry! No matter what type of triangle - big, small, acute, or obtuse - the three interior angles always sum to 180°.

What if my sum is close to 180° but not exact?

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In math problems, the sum must be exactly 180°. In real measurements, small differences might be due to rounding, but for theoretical problems, anything other than 180° means no triangle exists.

Can a triangle have an angle bigger than 90°?

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Yes! Obtuse triangles have one angle greater than 90°. But since all three angles must still sum to 180°, the other two angles must be quite small to compensate.

How do I spot that angles won't work before calculating?

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Look for warning signs: If you see an angle close to or over 120°, be suspicious! Also, if two angles already add up to more than 120°, the third would need to be negative.

What's the largest possible angle in a triangle?

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Just under 180°! As one angle approaches 180°, the other two must approach 0°, making the triangle extremely flat. In practice, angles are usually much smaller.

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