1.5.1

Angles in a Triangle

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Angles in a Triangle

The angles in a triangle add up to 180°. You can use this information to solve triangle problems.

The angles in a triangle add to 180°

The angles in a triangle add to 180°

  • So you need to subtract the sum of the given angles from 180 degrees to work out the missing angle.
Work out the sum of given angles

Work out the sum of given angles

  • You have been given the top angle - 45°.
  • We know that the other angle is a right angle by looking at it - that means it is 90°.
The sum of the given angles

The sum of the given angles

  • 90 + 45 = 135°.
Working out the missing angle

Working out the missing angle

  • So the missing angle is 180 - 135.
    • The missing angle is 45°.
Jump to other topics
1

Angles

1.1

7 Facts About Angles

1.1.1Facts About Angles1.1.2More Facts About Angles
1.2

Identify the Angle

1.2.1Identify the Angle
1.3

Angles on a Straight Line

1.3.1Angles on a Straight Line1.3.2Angles on a Straight Line - Practice Questions
1.4

Angles in a Circle

1.4.1Angles in a Circle
1.5

Angles in Triangles

1.5.1Angles in a Triangle
2

Fractions

2.1

Simplifying Fractions

2.1.1Simplifying Fractions2.1.2Identifying Equivalent Fractions
2.2

Improper Fractions & Mixed Numbers

2.2.1Improper Fractions & Mixed Numbers2.2.2Converting Mixed Numbers to Improper Fractions2.2.3Converting Improper Fractions to Mixed Numbers
2.3

Fractions of Numbers

2.3.1Fractions of Numbers
2.4

Expressing Shaded Areas as Fractions

2.4.1Expressing Shaded Areas as Fractions
3

Time

3.1

12-Hour & 24-Hour Clocks

3.1.1Difference Between 12-Hour & 24-Hour Clocks3.1.2Changing the 12-Hour Clock to the 24-Hour Clock3.1.3Changing the 24-hour Clock to the 12-Hour Clock
3.2

Time-Related Problems

3.2.1Time-Related Problems3.2.2Timetable & Schedule Problems
4

Prime Numbers

4.1

Prime Numbers

4.1.1Prime Numbers
5

Probability

5.1

Probability

5.1.1Probability Scale5.1.2Probability Fractions5.1.3Experimental Probability
6

Ratio

6.1

Ratios

6.1.1Ratios
7

Sequences

7.1

Constant Sequences

7.1.1Constant Increase Sequences7.1.2Constant Decrease Sequences
7.2

Doubling & Halving Sequences

7.2.1Doubling Sequences7.2.2Halving Sequences
7.3

Alternating Patterns & Two-Step Sequences

7.3.1Alternating Pattern Sequences
7.4

Two-Step Patterns

7.4.1Two-Step Patterns
7.5

The nth Term

7.5.1Find the nth Term7.5.2Using the nth Term
8

Area & Perimeter

8.1

Perimeter of a Quadrilateral

8.1.1Finding the Perimeter of a Quadrilateral8.1.2Finding the Missing Length
8.2

Area of a Quadrilateral

8.2.1Finding the Area of a Quadrilateral8.2.2Finding the Missing Side of a Rectangle8.2.3Finding the Missing Side of a Square8.2.4Finding the Area of Irregular Shapes
8.3

Area of a Triangle

8.3.1Finding the Area of a Triangle

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    What do the angles in a triangle add up to?Multiple choice
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Angles in a Circle

Simplifying Fractions