From what we have learned we already know the method about finding the area of a square, a rectangle, a triangle, a circle and so on. We can apply the formula that works for each form which is related to get the area.
Right now if we want to find the area of any forms like a stain on clothes. There is no related formula for anomalous forms to find its area; however, we can transfer the form into those shapes that we already know.
By using these known forms area we can get a similar area of an anomalous form. In order to get the value of the area more accurate to the actual anomalous form area, we can cut the area into as many known pieces as we want.
like these rectangles
This method can also be used for finding the area under a curve. As the image shows below: 
To get the area closer to the real area, we can use more and more rectangle to separate the area under the curve, like the image below:
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Tony Luo 44410165
Helen Zhang 31019169