Derive provides the menu items S implify , E xpand , and F actor to simplify expressions in which special functions like trigonometric functions, logarithm, and exponential occur. Derive is very precise in checking whether transformations of formulae are valid or not on the domain of computation. V ariable command and restrict the domain of a variable. For functions with simplification rules in two directions such as the rule you also have to specify the direction via the M anage menu item.
Examples show best what can be achieved.
Let us consider the transformation in both directions. Derive refuses to do the transformation unless the necessary condition is satisfied. V ariable command and specify x as a nonnegative number. Next, we issue the M anage L ogarithm command to control the direction of simplification and choose the Expand option. L ogarithm menu must be chosen to S implify in the opposite direction and combine sum of logarithms into the logarithm of a product.