Establish the following Identities

• January 17th 2011, 06:43 PM
IDontunderstand
Establish the following Identities
$\frac{\sin[x]}{\tan[x]} +\cos[x]=\sec[x]$
I can get this to be 2 cos x = sec x

I cannot see how to get those equal
• January 17th 2011, 06:49 PM
dwsmith
Quote:

Originally Posted by IDontunderstand
$\frac{\sin[x]}{\tan[x]} +\cos[x]=\sec[x]$

$\displaystyle\frac{\sin{x}}{\frac{\sin{x}}{\cos{x} }}+\cos{x}=\cos{x}+\cos{x}=2\cos{x}$

I don't know how you are going to get sex{x} out of that though :(
• January 17th 2011, 07:29 PM
IDontunderstand
Quote:

Originally Posted by dwsmith
$\displaystyle\frac{\sin{x}}{\frac{\sin{x}}{\cos{x} }}+\cos{x}=\cos{x}+\cos{x}=2\cos{x}$

I don't know how you are going to get sex{x} out of that though :(

Thank you. That is what I was thinking. Maybe it is a typo.
• January 18th 2011, 02:45 AM
Ackbeet
I agree with dwsmith. If you plug in $x=20^{\circ},$ you get an inequality.