Flashcards · Maths · Transformations and Similarity
Congruence and Similarity
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What are congruent shapes?
Shapes with exactly the same size and shape.
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What are similar shapes?
Shapes with the same shape but not necessarily the same size.
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What are the conditions for congruent triangles?
SSS, SAS, ASA and RHS.
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What does SSS mean?
All three sides are equal.
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What does SAS mean?
Two sides and the angle between them are equal.
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What does ASA mean?
Two angles and a side are equal.
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What does RHS mean?
A right angle, the hypotenuse and another side are equal.
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Why is AAA not enough for congruence?
The triangles could be different sizes.
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What do you give in a congruence proof?
Each equal pair with a reason, and the condition.
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What reasons can you use for equal sides or angles?
Given, common side, vertically opposite angles, or alternate angles.
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How do you find the scale factor for similar shapes?
Divide the length on one shape by the matching length on the other.
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If two angles of a triangle are equal to two of another, are the triangles similar?
Yes, because the third angles are equal too.
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What is the area scale factor if the length scale factor is \(k\)?
\(k^2\) (Higher tier).
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What is the volume scale factor if the length scale factor is \(k\)?
\(k^3\) (Higher tier).
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Two similar shapes have areas in the ratio \(4 : 9\). What is the ratio of their lengths?
\(2 : 3\) (Higher tier).
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What are corresponding sides?
Sides in the same position on similar shapes.