View Full Version : Proving trigonometric identities solver?
hanzel
Feb 4, 2012, 03:54 AM
Please prove if these two are identity ty.
http://www.mytrigonometry.com/math_image.aspx?p=SMB02FSMB03cot(x)SMB10csc(x) 1SMB02fSMB03SMB01sec(x)-tan(x)?p=199?p=42
Aurora2000
Feb 4, 2012, 07:53 AM
\frac{\cot x}{\csc x+1}=\sec x-\tan x
\frac{\cot x}{\csc x+1}=\frac{1}{\tan x(\csc x+1) }=\frac{1}{\tan x\csc x+\tan x}
Now \tan x\csc x=\tan x\sin^{-1} x=\cos^{-1} x=\sec x , thus
\frac{1}{\tan x\csc x+\tan x}=\frac{1}{\sec x+\tan x}
Now you have to prove
\frac{1}{\sec x+\tan x}=\sec x-\tan x .
Multiplying both sides by \sec x+\tan x this becomes
1=\sec^2x-\tan^2x =\frac{1}{\cos^2x}-\frac{\sin^2x}{\cos^2x}=\frac{1-\sin^2x}{\cos^2x}
and using 1=\sin^2x+\cos^2x you conclude.
Jmiller23
Mar 12, 2012, 06:49 PM
sec^4x-sec^2x=tan^4x+tan^2x
trigster
Apr 21, 2012, 06:28 AM
sin2x=2tanx/(1+tan^2x)
wendyjewel
Jun 9, 2012, 01:14 PM
4sin^2x+2cos^2x
jamesjonesmiami
Oct 16, 2012, 05:35 PM
I need to find the proof cot^2-1/csc^2=1-2sin^2
ebaines
Oct 17, 2012, 06:05 AM
i need to find the proof cot^2-1/csc^2=1-2sin^2
You have mistated the identy: it should be (cot^2-1)/csc^2 = 1-2sin^2
As always, it's best to replace the cot and csc functions with their sin and cos equivalents. Then it comes right out if you apply one of the standard iidentities that you should know be heart: cos^2 + sin^2 = 1