which function equivalent to reduce q modulo p?

a long equation has many Ei

how to convert into Gamma function using below identity

Ei(a, z) = z^(a-1)*GAMMA(1-a, z);

int(cos(a*z)/(z^2-4*z+8), z, method=contour)

why run in maple 15, unknown options method = contour

is it default to use contour?

but the result is the same as done by hand, i mean the answer from the book,

int(cos(a*z)/(z^2-4*z+8), z) return contain some Si  and Ci

Any Example can help see the difference between contour and simple integration?

int(XXXX, x, method = contour);

int (XXX, x)

which example can help to see the difference?

How to make maple to change ln(exp(x)) = x?  for example exp(ln(x)) = x, or ln(exp(x+1)) = x+1