Maths problem

Dist

Dist

Dist

Soldato
Joined
1 Jun 2005
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5,152
Location
Kent
Yes, this is yet another maths problem on a PC related forums, but im desperate for help as my OU books are rubish in this area tbh, and after trying to look online ive had basicaly no luck.

My problem is, i have to solve this equation using my calculator (set in radians) to 3dp, the equation is x + 2sin(x) = 2

now, since i couldnt figure out how im ment to arrive at the answer the correct way, i went through trial and error (ie, guessing) and know that the answer is roughly x=0.704, but i need help as to how im ment to correctly work it out.
 
Sorry about the long winded explanation... ask if there's anything that I haven't made clear enough.. which would be most of it judging by the length of it

You need to do it iteratively.

Rearrange the equation to make x the subject.
x + 2sin(x) = 2

2 possibilities
x = 2 - 2sin(x)
or
x = asin(1-x/2)

Start with 0.7 seen as that's pretty close judging by your answer.

Now the part you seem not to know is how to do the iterative method. So,
Punch 0.7 into your calc and press =
now write the equation out using the Ans button instead of x
So you get asin(1-Ans/2)

Each time you press equals it will update the answer and then use the new answer in the equation so you don't keep changing it manually.

Doing the above with the first possible equation x diverges so try the second. That one converges at a value of x=0.70457....
So, to 3 decimal places you get 0.705.
 
Great, thankyou Coran that helped a lot. I wish the books i have explained it like that as i can finaly manage to do it now :D
 
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