# Need a basic help

1. Apr 24, 2005

### beluluk

need a "basic" help

this may be a silly question... but, i really need this, because a basic is the stairway to the advanced of course.
i thought that this forum may provide more help than i could get in my college.
how do we find an answer of "sin(theta)" without an electronic device (such as calculator or computer). Can we do it manually, mathematically?
i thought that a calculator never needs a calculator's calculator to get the number. So i think there must be a way. thanks b4.

2. Apr 24, 2005

### dextercioby

There are tables of "sin" function values.Computed by hand using Taylor (MacLaurin)series expansion.If u don't find them,then u can compute them using the series expansion.I remember seing some logarithm tables for "sin" & "cos"...

Daniel.

3. Apr 29, 2005

### beluluk

ow... yeah... that reminds me of my lesson at the college. But i do hope there is a shorter way for that. anyway. Thanks a lot...

4. Apr 29, 2005

### matt grime

You won't do it manually mathematically. It is tedious (though possible) to obtain an answer to any degree of precision given enough time. Just as one could square any number by hand given enough time. But why would you?

5. Apr 29, 2005

### eNathan

Well, if you want a computer to do it, you could write A batch file? Why would you need this to be done in the first place tough>? :uhh:

6. Apr 29, 2005

### Staff: Mentor

When I was in high school, hand-held electronic calculators hadn't been invented yet, and desktop ones were very expensive. I didn't use an electronic desktop calculator until I started college. So for calculations I had a book of trig and log tables. The sine table probably had entries for at least every 0.1 degree, or perhaps every 5 minutes of arc (1/12 degree). I remember doing linear interpolation between entries, by hand, to eke out an extra significant figure.

7. Apr 30, 2005

### bahamut

Just draw a triangle,then you measure it!
It may not be very accurate,but it is a way!

8. May 11, 2005

### beluluk

i need to think about it since i was looking for an operation of 3D angles. when i got a vector which is stated in spheric coordinates, suppose i the vector components are r1, phi1 and theta1. how can i find the angle between the vector and the x axis.... but i think i know the answer now. I can use the dot product to find it.thanks for asking.