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# Iterative Formula - C3 watch

1. Was wandering if anyone could help me with the following:

Using Xn+1=(1-Xn)/cos(Xn) with X1=0.5 find the limit of the sequence X1,X2,X3... to 2 dp.
(The n+1 and n after X are subscript)

I know how to find X1, X2, X3 etc. but am not sure how to find the limit, Thanks!
2. Just keep going 'til you get to a point where the value to 2dp stays the same. If you're not sure try putting the upper and lower bounds into the original function and see if there's a change in sign.
3. But all the first five terms come to 0.50000000????? and one term goes up then the next goes down
4. If your first five terms come to that then your answer is simply 0.50 to 2dp, exam questions won't really ask you to go very far. And yes sometimes the value can 'bounce' around a bit, but it will still come to rest on the 'true' value.
5. Okay, easier than I thought , Thank you

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