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adjacent
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Homework Statement
We know the if two 2D shapes are similar, the ratio of their areas are equal to the ration of the square of the corresponding sides.
##\frac{A_2}{A_1}=(\frac{l_2}{l_1})^2##
Prove this
The Attempt at a Solution
For rectangles:
Let the area of first rectangle be ##A_1## and the 2nd rectangle be ##A_2##.
Let the sides of 1st rectangle be l and b and the second rectangle be ##l_2 \text{ and b_2}##.
1st rectangle......Second rectangle
Area=lb......Area= ##l_2b_2## we know that ##l_2## is kl and ##b_2## is kb
So ##klkb=k^2lb##
Which means that Area of larger rectangle is ##k^2 \times##area of smaller rectangle.
Area=##k^2lb##
Therefore, ##l_2b_2=k^2lb## So ##k^2=\frac{l_2b_2}{lb}##(in other words ##\frac{A_2}{A_1}##
So ##\frac{A_2}{A_1}=k^2## and we know that ##k=\frac{l_2}{l_1}=\frac{b_2}{b_1}##
So ##\frac{A_2}{A_1}=(\frac{l_2}{l_1})^2##
But how do we know that this is general for ALL the 2D shapes?