# Solve equations with sin(x)

Hi. I want to know why sage can't solve the euqations: [4sin(x)+y==5,sin(x)==y] (It's so easy!)and it just gives back: [sin(x)==y,y+4sin(x)==5]. Can you help me?

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What command did you give?

( 2014-08-01 11:51:38 -0600 )edit

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Congratulations, you have found a bug! I have reported it at

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Solving equations is done through the solve command, which is documented here. I went to a Sage cell server and typed in:

solve(5-4*sin(x)==sin(x),x)


and got an answer: [x == 1/2*pi]. Of course, since the trig functions are periodic there are an infinite number of solutions.

Since you haven't given the code that resulted in the output you describe, it's impossible for me to know what went wrong. Always provide your code; it makes it easier to diagnose what is wrong.

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On sagenb.org using var('x,y'); solve([y==sin(x),y+4*sin(x)==5],x,y) I get [y == sin(x), y + 4*sin(x) == 5] as a solution

( 2014-08-03 06:32:21 -0600 )edit