# Trigonometric Identites

Printable View

• December 11th 2007, 06:31 AM
spedman
Trigonometric Identites
I need some help on 15 identites problems to help me study for my math final.

they range from problems like

sec^2x csc^2x = sec^2x + csc^2x

to

tan(pi/5) - tan(pi/30) = (-1/root 3)
1+tan(pi/5) tan(pi/30)

Anyone think they would be able to help me?
• December 11th 2007, 06:36 AM
kalagota
when is your finals? and how do you want us to help you?
• December 11th 2007, 06:37 AM
spedman
my final is on thursday. and anything anyone could really do would be great. whether it be do the problems out, or help me figure out how to start it.
• December 11th 2007, 06:48 AM
kalagota
ahh, so you want us to solve the problems you gave above..

so, i think, the first one is easy.. note that $\sec^2 x = tan^2x + 1$ and $\tan^2 x = \frac{\sin^2x}{\cos^2} =\frac{\sec^2x}{\csc^2x}$, so ithink, you can do it..
• December 11th 2007, 06:51 AM
kalagota
for the other one, take note of sum/difference in tangents.

$\tan (A \pm B) = \frac{\tan A \pm \tan b}{1 \mp \tan A \tan B}$

so can you recognize that $A = \frac{\pi}{5}$ and $B = \frac{\pi}{30}$?
• December 11th 2007, 08:04 AM
spedman
They are blurry and somewhat hard to read, but if anyone wants to take a crack at some of them they are here:

http://img407.imageshack.us/img407/5696/math1lh2.jpg

http://img509.imageshack.us/img509/9642/math2fw6.jpg

http://img70.imageshack.us/img70/7996/math3hn7.jpg

http://img69.imageshack.us/img69/7543/dsc00180on3.jpg

15 problems. If anyone can't read something just let me know.