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# fp1 linear interpolation watch

1. f(x)=tanx+1-4x,Π/2<X<Π/2
Show that f(x)=0 has a root in the interval [1.42,1.44]
I tried to put calculator in radian mode but it didn't work
2. (Original post by alesha98)
f(x)=tanx-1-4x,Π/2<X<Π/2
Show that f(x)=0 has a root in the interval [1.42,1.44]
I tried to put calculator in radian mode but it didn't work
Fixed it for you.
3. (Original post by alesha98)
f(x)=tanx+1-4x,Π/2<X<Π/2
Show that f(x)=0 has a root in the interval [1.42,1.44]
I tried to put calculator in radian mode but it didn't work
http://www.thestudentroom.co.uk/forumdisplay.php?f=38
4. (Original post by alesha98)
f(x)=tanx+1-4x,Π/2<X<Π/2
Show that f(x)=0 has a root in the interval [1.42,1.44]
I tried to put calculator in radian mode but it didn't work
What's f(1.42)?

What's f(1.44)?

Moved to maths.
5. You know it's continuous due to the domain of the function, so just check f(1.42) and f(1.44) and if there's a change of sign then there must be a root within the interval.
6. (Original post by Zacken)
What's f(1.42)?

What's f(1.44)?

Moved to maths.
I got f(1.42)=19011 but it isnt the answer
7. (Original post by alesha98)
I got f(1.42)=19011 but it isnt the answer
What are you putting into your calculator?
8. (Original post by alesha98)
f(x)=tanx+1-4x,Π/2<X<Π/2
Show that f(x)=0 has a root in the interval [1.42,1.44]
I tried to put calculator in radian mode but it didn't work
(Original post by EricPiphany)
Fixed it for you.
^^ notice you wrote "+1", however it should be "-1" as the above poster said.
9. I double checked from the book and the question is tanx+1-4x.
I put calculator in radian mode:tan1.42+1-4(1.42)
10. (Original post by alesha98)
I double checked from the book and the question is tanx+1-4x.
I put calculator in radian mode:tan1.42+1-4(1.42)
That's a typo in the book then. It works with tan(x)-1-4x (root at ~1.422).
11. (Original post by alesha98)
I double checked from the book and the question is tanx+1-4x.
I put calculator in radian mode:tan1.42+1-4(1.42)
its probably a mistake in the book, answer tanx - 1 -4x instead

so it must be -1 instead of +1

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