Euler's Question Problem causing... problems :/

[xkcirtap]

Hey there; I've been stumped on this question for awhile now; I can't seem to get the answer:

Let dy/dx = 2 arcsin (x-1) and (x0, y0) = (0,1).
Using Euler's method, with a step size of 0.2, the value of y2 would be given by...?

I get the method but for some reason I'm not getting the desired answer provided in the multiple choice. Help would be much appreciated!

[Vincezor]

y1 = 1 + 0.2*arcsin(-1)

y2 = (1+0.2*arcsin(-1)) + 0.2*arcsin(0.2-1)



Is this the correct answer? :S

[xkcirtap]

Not too sure; the multiple choice answers given are in exact numbers. If you like; I'll type up the choices? or the exact form of the answer?

[Vincezor]

is what I get on my CAS...

[xkcirtap]

It's pretty close unless I'm looking at your answer wrong: The answer is 1-(pi/5) - 0.4arcsin(0.

[xkcirtap]

er that's a arcsin(0.8 ) at the end... emoticons :@

[jaz_rocks_123]

What's wrong with that answer?

step 1:

1+2/5*arcsin(-1)
=1-pi/5

Step 2:
1-pi/5+2*0.2*arcsin(0.2-1)
=1-pi/5-0.4arcsin(0.8 )

[xkcirtap]

Nothing; but whilst working out; I couldn't get exact values on my calculator and hence had no idea how to even get that number. I think it has something to do with the fact that I'm typing in 'csc(x)' for arcsin... Still, thanks for showing that step by step process

Edit: Just realised csc wasn't arcsin == However, even when typing in arcsin; I get a decimal not an exact number.

Edit (2): Okay figured it now; it was because I keep writing 0.4; I tried 2/5 and it works. Thanks Jaz!

[Andiio]

Nothing; but whilst working out; I couldn't get exact values on my calculator and hence had no idea how to even get that number. I think it has something to do with the fact that I'm typing in 'csc(x)' for arcsin... Still, thanks for showing that step by step process

Edit: Just realised csc wasn't arcsin == However, even when typing in arcsin; I get a decimal not an exact number.

Edit (2): Okay figured it now; it was because I keep writing 0.4; I tried 2/5 and it works. Thanks Jaz!

Which calc are you using?

[abeybaby]

Even if you get decimals its fine, just plug all the choices into your calc and see which ones match up