# Solving a trig equation.

• May 29th 2011, 09:56 AM
Ellla
Solving a trig equation.
Find the maximum(minus) answer of this equation:

(sinx-2)(cosx+ $\frac{\sqrt{3}}{2}$ )=0

Is it - $30^0$?

Thanks.
• May 29th 2011, 10:30 AM
Also sprach Zarathustra
sinx-2 is never zero.

so you left with:

cosx=-sqrt(3)/2)

can you find the solutions for that?
• May 29th 2011, 11:45 AM
Quote:

Originally Posted by Ellla
Find the maximum(minus) answer of this equation:

(sinx-2)(cosx+ $\frac{\sqrt{3}}{2}$ )=0

Is it - $30^0$?

Thanks.

There is a minimum at -30 degrees, yes.
However, there are also solutions to f(x)=0.

Are you looking for the graph minimum or solutions to f(x)=0 ?
• May 29th 2011, 12:01 PM
Ellla
Quote:

Originally Posted by Also sprach Zarathustra
sinx-2 is never zero.

so you left with:

cosx=-sqrt(3)/2)

can you find the solutions for that?

x = $\frac{\pi}{6}$ +2 $\pi$ k...and what should I do next?

Well, the answer is degrees and I am looking for maximum not min. Thank you.
• May 29th 2011, 12:26 PM
Quote:

Originally Posted by Ellla

Well, the answer is degrees and I am looking for maximum not min. Thank you.

You did mention a "negative maximum",
so are you looking for a point on the graph furthest below the x-axis?
Also, if you are looking for a maximum of any kind,
solving f(x) = 0 doesn't find it.

The most negative value is a minimum.
• May 29th 2011, 01:19 PM
Ellla
Quote:

You did mention a "negative maximum",
so are you looking for a point on the graph furthest below the x-axis?
Also, if you are looking for a maximum of any kind,
solving f(x) = 0 doesn't find it.

The most negative value is a minimum.

Yes, sorry for not explaining properly what I was looking for.

Quote:

so are you looking for a point on the graph furthest below the x-axis?
Yes.
• May 29th 2011, 01:33 PM