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| Similarity |
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| Study the following figures. They have the same shape though their sizes are different. One figure is the enlargement of the other figure. |
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| These figures are said to be similar to each other. In our study, we mostly deal with similarity of triangles. |
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| Two triangles are similar if |
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| (i) Their angles are the same and |
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| (ii) The corresponding sides are proportional |
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| (i) ÐA =
ÐX, ÐB =
ÐY and ÐC =
ÐZ |
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(ii)  |
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| The symbol for similarity is '~', |
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 For the above case, |
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| DABC is similar to
DXYZ. |
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| (i) If two triangles are congruent, then they are similar. Its converse is not true. |
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(ii)  = a constant. |
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| Let the constant be equal to K. Then K is called enlargement factor (or the dilation factor/scale factor/magnification factor). AB is K times XY and so on. |
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