(iii)
Usually, if any function is a power of x or a polynomial in x, then we take it as the
first function However, in cases where other function is inverse trigonometric
function or logarithmic function, then we take them as first function Example 18 Find log x dx
∫
Solution To start with, we are unable to guess a function whose derivative is log x We
take log x as the first function and the constant function 1 as the second function