Method 2: subtraction. Subtract the area of the whole figure from the area of the non-shadow part to get the area of the shadow part.
Method 3: auxiliary line method. By making auxiliary lines, complex figures are simplified, and figures that can directly calculate the area are formed, such as triangles, parallelograms, trapeziums, etc.
Method 4: Digging and filling method. Irregular figures are converted into regular figures by digging and filling method for calculation.
Method 5: Equal product transformation method. The complexity is simplified and the shadow area is calculated through the equal product transformation between plane graphics.
1, find the area of the shaded part in the trapezoid. (Unit: cm)
(32+ 18)× 15÷2-32× 15÷2
=375-240
= 135 (square centimeter)
A: The shadow area is 135 cm2.