- #1

jacki

- 3

- 0

__backward euler__implicit method by Newton-raphson iteration. The differential equation is for a simple planar pendulum. So the function for the pendulum is :

**(1)**angularAcceleration (angle) = ( -gravity/length ) * sin(angle);

and the update function for implicit integration is:

**(2)**u_(t+1) = u_t + deltaTime * velocity_(t+1)

velocity_(t+1) = velocity_t + deltaTime * angularAcceleration ( u_(t+1) )

__My question is:__given that Newton's method is stated as x_(i+1) = x_i - f( x_i) / f ' (x_i) ,

what is the f in Newton's method? Is it the residual of the pendulum function given by

**(1)**or the residual of the update step given by

**(2)**?

Thanks in advance!