Use the sketch to split the shaded region into curved and straight-edged pieces, then add or subtract their areas.
Horizontal line: \(A=\displaystyle\int_a^b y\,\mathrm{d}x-\text{area of rectangle}\)
Sloping line: \(A=\displaystyle\int_a^b y\,\mathrm{d}x-\text{area of triangle (or trapezium)}\)
| Shape | Area |
|---|---|
| Rectangle | |
| Triangle | |
| Trapezium |
Integrating a straight-line boundary is equally valid. Use perpendicular heights in the geometric formulae.
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