# Thread: Desparate trig help needed

1. ## Desparate trig help needed

I don't even know where to start with this question:

if arccos(x)= -1 then what does the csc(x) = ?

Also: find solutions of equation [in form of theta + 2pik, 0<theta<2pi ] for

2cos(x)-sq.rt.of 3=0

Again, I don't even know where to begin.

Thanks anyone.

2. Originally Posted by jd981
I don't even know where to start with this question:

if arccos(x)= -1 then what does the csc(x) = ?
You are supposed to know that

$\cos(\arccos(x)) = x$. That means:

$x = \cos(-1)$

Since $\csc(x)=\dfrac1{\sin(x)}$ you'll get:

$\csc(x)=\dfrac1{\sin(\cos(-1))} \approx 1.944$

Also: find solutions of equation [in form of theta + 2pik, 0<theta<2pi ] for

2cos(x)-sq.rt.of 3=0

...
$2\cos(x)-\sqrt{3}=0~\implies~ \cos(x)=\frac12 \sqrt{3}~\implies~x=\frac \pi6~\vee~x=2\pi-\frac \pi6$