There is a link in post #7 and the post #8 looks promising.

]]>Does such formula exist?

Well, I suggest this method (an Impossible and stupid one):

`Draw a right angled triangle with :theta = 5, and find the ratio of the Perpendicular and Hypotenuse`

]]>

Why? Have you tried as hard as you could?

]]>P.S.

IDK i drag at math

It should be pretty fast, since dividing by 3 on each step will drop the argument to arbitrarily small size in logarithmic time. Of course, don't compute sin(x/3) twice in every iteration!

Here's a proof that it works:

]]>While looking for something else I found this page and remembered your post.

This guy is doing what we thought was impossible, Turned out Ptolemy and Archimedes solved this problem satisfactorily, without calculators or Taylor series, Pade approximants or Cordic. Just from knowing a few trig relations and some values of common angles. You should be able to get as close to sin(5°) as you wish,

http://www.marypat.org/stuff/nylife/010206.html

Just go past the first part that deals with Taylor series.

]]>Relatively Quantum has a point. Since some calculators (Texas Instruments- I think, I remember reading about it and HP) have abandoned Economized Taylor series and even Pade approximants in favor of that old Cordic algorithm which uses rotations to calculate. But it does need a table lookup initially so it violates one of his restrictions.

]]>Since it's actually 15 though, it's easy enough to just use the half-angle formula on 30.]]>

Actually, I too did the same and got an equation of 3rd power with complex roots :-)

But the problem is, I need this for my daughter who is in class 8 and they haven't learned complex numbers as yet....

I think that the teacher made a mistake in the question paper - she wrote 5 instead of 15 :-)]]>

Pls. help me find a way to calculate values like sin 5 & cos 10 ( the arguments are in degrees) without using tables or series...Just common formulas from grade 7-8 trignometry!!!]]>