Year 7

Interior and exterior angles of triangles

Free examples and worked answers. No account needed.

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Practise the method.

Example 1

Find the third angle
Find the third angleAn isosceles triangle has two equal base angles, each 40°. The angle x° is at the top. Matching ticks identify the two equal sloping sides. Diagram not to scale. Use the labelled measurements.40°40°x°
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Answer:

Example 2

Find the exterior angle
Find the exterior angleA triangle has 40° at the lower-left vertex and 60° at the top. Its horizontal base extends past the lower-right vertex. The exterior angle x° is between this extension and the side leading to the top. Diagram not to scale. Use the labelled measurements.40°60°x°
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Answer:

Example 3

Find the third angle
Find the third angleAn isosceles triangle has two equal base angles, each 60°. The angle x° is at the top. Matching ticks identify the two equal sloping sides. Diagram not to scale. Use the labelled measurements.60°60°x°
Show worked answer

Answer: