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Aitken Formula

The iteration xk=0.9−sin(xk−1) converges for starting values x0 ∈ [0.15,1]. This question guides you through a solution method we haven't met so far. Enter all results to at least 6 significant figures.

1.1
Starting with x0=0.4, compute x1 using fixed point iteration.

1.2
Compute x2.

1.3
Now use the Aitken acceleration formula to compute r0 from x0, x1, x2.
r0=

1.4
Compute r1 from r0 using fixed point iteration (NOT the Aitken formula).

I got 1.1,1.2 and 1.3 but there is no relationship between r1 and r0 so I don't see how you can find r1 using an iterative method. Surely you can just find x3 and then use the Aitken formula?