Integrals of class of functions following a definite pattern can be found by the method of reduction and recursion. Reduction formulas make it possible to reduce an integral dependent on the index n>0, called the order of the integral, to an integral of the same type with a smaller index. Integration by parts helps us to derive reduction formulas. (Add a constant in each question). If In,m=∫cosmxsinnx then, In,m+m−1n−1In−2,m−2 is equal to -
(a) cosm−1xsinn−1x
(b) (m−1)1cosm−1xsinn−1x
(c) (n−1)1cosm−1xsinn−1x
(d) m−1n−1cosm−1xsinn−1x