Triangles and Interior & Exterior Angles

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Questions and Answers

What type of triangle has three acute angles?

  • Obtuse triangle
  • Right triangle
  • Equilateral triangle (correct)
  • Isosceles triangle

Which type of triangle contains an obtuse angle?

  • Equilateral triangle
  • Isosceles triangle
  • Right triangle (correct)
  • Acute triangle

How many sides of equal length does an isosceles triangle have?

  • Two (correct)
  • Four
  • One
  • Three

Which type of triangle has exactly one obtuse angle?

<p>Isosceles triangle (D)</p> Signup and view all the answers

What are the angles within a triangle called?

<p>Interior angles (D)</p> Signup and view all the answers

What is the sum of the interior angles of any triangle?

<p>$180$ degrees (D)</p> Signup and view all the answers

Why do all triangles have a total measurement of $180$ degrees?

<p>Because a straight angle measures $180$ degrees. (C)</p> Signup and view all the answers

In an equilateral triangle, how much is the measurement of each angle?

<p>$60$ degrees (A)</p> Signup and view all the answers

If one angle in an isosceles triangle is $80$ degrees, what is the measurement of the other two angles?

<p>$40$ degrees each (C)</p> Signup and view all the answers

If angle A in a triangle measures $30$ degrees and angle B measures $60$ degrees, what is the measurement of angle C?

<p>$80$ degrees (C)</p> Signup and view all the answers

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Study Notes

Triangle Basics

  • A triangle is a shape with three points and three lines that intersect at these points, containing a total of three interior angles.
  • Interior angles are the angles within the triangle, and exterior angles are the angles that lie outside the triangle.

Types of Triangles

  • Right triangles contain a right angle (90°).
  • Acute triangles have three acute angles (less than 90°).
  • Obtuse triangles have one angle that is greater than 90° (obtuse angle).
  • Equilateral triangles have three equal sides and three equal angles.
  • Isosceles triangles have two sides of the same length and two angles with the same measurement.
  • Scalene triangles have sides that are all unique in size.

Angle Sum Property

  • The sum of the interior angle measurements within a triangle always equals 180°.
  • This is true for any and every triangle, regardless of type.

Why Triangles Have 180 Degrees

  • A straight angle is an angle whose measurement is exactly 180°.
  • If a straight angle is divided into three points, a triangle can be formed, and the sum of the interior angles still equals 180°.

Solving Unknown Angles

  • If one angle measurement is unknown, it can be found by taking the sum of the other two angle measurements and subtracting it from 180°.
  • Using the properties of the triangle type, one can also determine unknown angles.

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