Composite Mid-point method for numeric integration

Some numerical calculations and analysis exercises of Numeric Integration.

COMPOSITE midpoint rule method. Some numerical calculations and analysis exercises of Numeric Integration for comparison analysis. f function is given in terms of a symbolic variable x and expressed as an inline function. E.g., f=inline('x^2+2*x-2'). Also, if the function f is trigonometric function, the 4th argument can be entered as 'trigonom' or just 'trig' or 1. X is expected to be in degrees for trigonometric function evaluations. The number of steps NSTEPS has to be even. upl and lowl are upper and lower limits. NB: Sequence order of limits is unnecessary to follow, 'if' conditions will take care of lower and upper limits accordingly.