# Use taylor's THeorem to determine the accuracy

razored
Use taylor's THeorem to determine the accuracy of the approximation: cos(.3) ~=1 - (.3)^2 / 2! + (.3)^4 / 4! when i use taylors theorem, i use (.3)^4 / 4! which gets me 2.03e-10 but the asnwer is R<=2.03e-5

Homework Helper

(.3)^4/4! is not equal to 2.03e-10. What form of the remainder term are you using?

razored

Okay, it should be (.3)^5 / 5!

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razored

But i still don't get it, why did i get hte right answer and ignore the f^(n+1)(c) of the formula? (Lagrange error bound) The derivative should have been cos , so i must have picked cos 0. Why?