I want to solve a sinus equation.

Hi,

I want to solve this equation for X in a function with b, c and d as parameters :

b*sin(c)=d*sin(x)

Maybe i'm seeing this wrong, but I tried to solve for X using solve() but it gives me

>> s = solve(b*sin(y)=c*sin(x),x)
??? s = solve(b*sin(y)=c*sin(x),x)
                      |
Error: The expression to the left of the equals sign is not a valid target for an assignment.

Edit : I want a x between 0 and 2pi.

Thanks a lot,

Seb

Answer 1

[Matt Fig]

x = asin(b*sin(c)/d)

Or, if you want MATLAB to do it:

solve('b*sin(c)-d*sin(x)','x')

You want x to be on [0 pi]? You have three unknowns to work with, so that means you will have an infinite number of solutions.

How about b = 0, d equal to any nonzero number, and c equal to any number you want?

[Walter Roberson]

Or

syms x
solve(b * sin(c) - d*sin(x), x)

Answer 2

[Walter Roberson]

The ability to use "=" inside solve() was new in R2012a. You will need to use a technique such as shown in Matt's answer if you are using an older version.

Answer 3

[Teja Muppirala]

You're just forgetting the apostrophes

solve('b*sin(c)=d*sin(x)')

ans =

      asin((b*sin(c))/d)
 pi - asin((b*sin(c))/d)

[Teja Muppirala]

Or, if you want to use symbolic variables, use "==" instead of '='

s = solve(b*sin(y)==c*sin(x),x)

s =

      asin((b*sin(y))/c)
 pi - asin((b*sin(y))/c)