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fp1 linear interpolation

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 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.
Reply 2
Avatar for TeeEm
TeeEm
19
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
Reply 3
Avatar for Zacken
Zacken
22
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)?

What do you mean your calculators radian mode isn't working?

Moved to maths.
Reply 4
Avatar for TLDM
TLDM
6
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.
Reply 5
Avatar for alesha98
alesha98
OP
4
Original post by Zacken
What's f(1.42)?

What's f(1.44)?

What do you mean your calculators radian mode isn't working?

Moved to maths.


I got f(1.42)=19011 but it isnt the answer
Reply 6
Avatar for Zacken
Zacken
22
Original post by alesha98
I got f(1.42)=19011 but it isnt the answer


What are you putting into your calculator?
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.
Reply 8
Avatar for alesha98
alesha98
OP
4
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)
Reply 9
Avatar for TLDM
TLDM
6
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).
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

tan⁡(1.42) and tan⁡(1.44)≈7 \displaystyle \tan(1.42)\: \text{and}\: \tan(1.44) \approx 7 so it must be -1 instead of +1

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