Comparing Angles: Is an Acute Angle Less Than 90 Degrees?

Angle Classification with Size Comparisons

True or false?

An acute angle is smaller than a right angle.

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

True or false?

An acute angle is smaller than a right angle.

2

Step-by-step solution

The definition of an acute angle is an angle that is smaller than 90 degrees.

Since an angle that equals 90 degrees is a right angle, the statement is true.

3

Final Answer

True

Key Points to Remember

Essential concepts to master this topic
  • Definition: Acute angles measure less than 90 degrees exactly
  • Comparison: Right angle = 90°, so acute < 90° < obtuse
  • Check: Verify angle type: 45° is acute, 90° is right ✓

Common Mistakes

Avoid these frequent errors
  • Confusing acute and right angle definitions
    Don't think acute angles can equal 90 degrees = wrong classification! An angle that measures exactly 90° is called a right angle, not acute. Always remember acute means strictly less than 90 degrees.

Practice Quiz

Test your knowledge with interactive questions

a is parallel to b.

Calculate the angles shown in the diagram.

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FAQ

Everything you need to know about this question

What's the difference between acute and right angles?

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An acute angle measures less than 90 degrees, while a right angle measures exactly 90 degrees. Think of it like this: acute angles are 'sharp' and smaller than the corner of a square!

Can an angle be 89.9 degrees and still be acute?

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Yes! As long as an angle measures less than 90 degrees, it's acute. So 89.9°, 45°, 30°, and even 0.1° are all acute angles.

What comes after acute angles in size?

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The order goes: acute (less than 90°) → right (exactly 90°) → obtuse (between 90° and 180°) → straight (exactly 180°).

How can I remember what acute means?

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Think of the word 'acute' as meaning sharp or pointed. Acute angles look sharp and narrow, like the tip of a pencil - they're smaller than the square corner of a right angle!

Are there any tricks to identify acute angles quickly?

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Yes! Compare the angle to a right angle (like the corner of a book or square). If your angle looks smaller and more pointed than that corner, it's acute!

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