Saved Bookmarks
| 1. |
HiiFind the order of given Differential equation :-y = A sinx + B cos(x+c)__________________need a proper solution no spam :) |
|
Answer» Given that, y = A sinx + B cos (x + c) ...(i) To find the required differential equation and its order, we need to eliminate the ARBITRARY constants A, B and c So, DIFFERENTIATING both sides of (i) with respect to x, we get dy/dx = d/dx {A sinx + B cos (x + c)} ⇒ dy/dx = d/dx (A sinx) + d/dx {B cos (x + c)} ⇒ dy/dx = A cosx - B sin (x + c) ...(ii) Here, d/dx (sinx) = cosx d/dx (cosx) = - sinx d/dx {k f(x)} = k d/dx {f(x)}, where k is any constant d/dx {sin (MX + c)} = m cos (mx + c) d/dx {cos (mx + c)} = - m sin (mx + c) d/dx (u + V) = du/dx + dv/dx, where u and v are functions of x Again, differentiating both sides of (ii) with respect to x, we get d/dx (dy/dx) = d/dx {A cosx - B sin (x + c)} ⇒ d²y/dx² = d/dx (A cosx) - d/dx {B sin (x + c)} = - A sinx - B cos (x + c) = - {A sinx + B cos (x + c)} = - y, using (i) no. equation ⇒ d²y/dx² + y = 0 ...(iii) which is the required differential equation The order of the differential equation (iii) is 2 because the HIGHEST order of the derivative term d²y/dx² is 2 # |
|