As the name suggest, composite figure is composed of smaller standard figures whose area are known. You can use them and their sum will give you the area of the targeted composite figure.
Surface area are derived for some standard shapes like circle, triangle, parallelogram, rectangle, trapezoid, etc.
When some shape comes which isn't standard figure, then we find its area by slicing it (virtually, like by drawing lines) in standard shapes. Then we calculate those composing shapes' area and sum them all.
Thus,
[tex]\text{Area of composite figure} = \sum (\text{Area of composing figures})[/tex]
That ∑ sign shows "sum"
For example, take the figure attached below. We can split that figure in a triangle and rectangle. Then find their area and sum them to find the total area.
Total area of figure = [tex]\rm \: Area \: 1 + Area \: 2[/tex] sq. units.
Learn more about composite figure here:
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