View Full Version : Studying for a test and can't figure out some of the questions
DeweyFlash7
Nov 23, 2009, 10:00 PM
1.) 1/tanx+secx=cosx/sinx+1
2.) secx-tanx=1-sinx/cosx
3.) Usethe given informationtofind sin2x, cos2x, and tan 2x
cscx=-5/2 270<x<360
4.) Solve each equation for 0<x<360
cosxtanx=1/2
5.) Solve each equation for 0<x<2pie
Root 3 cotx=2cosx
Perito
Nov 24, 2009, 05:53 AM
These appear to be identities.
Memorize these important definitions:
A. tan(x) = \frac {sin(x)}{cos(x)}
B. csc(x) = \frac {1}{sin(x)}
C. sec(x) = \frac {1}{cos(x)}
Also, remember this important identity:
D. sin^2(x) + cos^2(x) = 1
Here's the first problem as you wrote it.
\frac {1}{tan(x)} + sec(x) = \frac {cos(x)}{sin(x)} + 1
1. using items (A), you'd get:
\frac {1}{\frac {sin(x)}{cos(x)}} + sec(x) = \frac {cos(x)}{sin(x)} + 1
and
\frac {cos(x)}{sin(x)} + sec(x) = \frac {cos(x)}{sin(x)} + 1
This would only be true if sec(x) = 1, but that's not possible for all x. I believe you entere the problem incorrectly.
For the others, do the same substitutions. Try to manipulate the equations so that what you see on the left is the same as the right. This is how you prove identities.
Unknown008
Nov 24, 2009, 08:11 AM
It might and could be 'solving' and not proving. The only problem is that it didn't mention the interval in 1 and 2 in contrast with the others.
Also, \pi is written as 'pi' and not 'pie' as in 'apple pie'.