Differentiation Problem

Hello,

I am working from a Naval Architecture book which gives a problem to which I want to use MatCAD Prime to go through the problem myself (as the book has no explanation).

The initial expression is:

KM=0.5T+B^2/12T

Where the expressions are:

KM is a naval arch term which represents the distance from the Keel of a ship to the Metacentre

B is the Breadth of the Ship

T is the Draught.

The book gives a plot of the above expression for a ship with a breadth (B) of 15 and shows how as T increases KM reduces to a point.

The book goes on to state that you can find the draught (T) when KM is at its lowest value by differentiating the above expression with respect to T and equating to zero. It then gives this as:

dKM/dT = 0.5-B^2/12T^2

and states in the example of a ship with B of 15 the answer would be 6.12.

I however cannot work out how this was derived or how to use MatCAD to solve such a problem.

Any advice warmly welcomed.

Andy