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Vector Algebra

Question
CBSEENMA12032863

Verify that the function y = a cos x + b sin x, where a, b ∊ R is a solution of the differential equation fraction numerator straight d squared straight y over denominator dx squared end fraction plus straight y space equals space 0.

Solution

                          straight y space equals space straight a space cosx space plus space straight b space sinx                          ...(1)
           therefore space space space dy over dx space equals space minus straight a space sinx space plus space straight b space cosx
rightwards double arrow space space space space fraction numerator straight d squared straight y over denominator dx squared end fraction space equals space minus straight a space cosx space minus space straight b space sinx
rightwards double arrow space space space fraction numerator straight d squared straight y over denominator dx squared end fraction space equals space minus straight y space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space open square brackets because space space of space left parenthesis 1 right parenthesis close square brackets
rightwards double arrow space fraction numerator straight d squared straight y over denominator dx squared end fraction plus straight y space equals space 0
therefore space space space straight y space equals space straight a space cosx space plus space straight b space sinx is a solution of the differential equation
                      fraction numerator straight d squared straight y over denominator dx squared end fraction plus straight y space equals space 0.