110 likes | 346 Views
The Trapezium Rule. When we can’t integrate. Find the shaded area. We don’t know how to integrate this function, so we can use trapeziums to make an estimate. So can divide this area up into 4 trapeziums of equal width. Area of a Trapezium. Area = ½ (a + b) h. a and b are the parallel sides
E N D
The Trapezium Rule When we can’t integrate...
We don’t know how to integrate this function, so we can use trapeziums to make an estimate So can divide this area up into 4 trapeziums of equal width
Area of a Trapezium Area = ½ (a + b) h a and b are the parallel sides h is the width
How do we find the height of each side of the trapeziums? The height of each trapezium can be found by substituting the x value into the function to get y y2 y3 y4 y1 y0
Total Area = y2 y0 y1 y3 y4 h h h h ½ (y0 + y1)h + ½ (y1 + y2)h + ½ (y2 + y3)h + ½ (y3 + y4)h
Total Area = ½ (y0 + y1)h = ½ h [(y0 + y1) + (y1 + y2) + (y2 + y3) + (y3 + y4)] = ½ h [y0 + y1 + y1 + y2 + y2 + y3 + y3 + y4] = ½ h [y0 + 2(y1 + y2 + y3 ) + y4] + ½ (y1 + y2)h + ½ (y2 + y3)h + ½ (y3 + y4)h
TRAPEZIUM RULE = ½ h [y0 + 2(y1 + y2 + y3 ) + y4] In general, for any area divided up into n trapezia of equal width = ½ h [y0 + 2(y1 + y2 + ... + yn-1 ) + yn]