Solve the Trig equation

flakine

Junior Member
Joined
Aug 24, 2005
Messages
78
tan x +sec x =sqrt3

I have:

sin/cos + 1/cos =sqrt3

(sin+1)/cos=sqrt3

now what?
 
What happened to your x's?

What is the value of "x"?

(Note: This equation is not true in general. For instance, let x = 0.)

Eliz.
 
My mistake:

sin x/cos x+ 1/cos x=sqrt3

(sin x+1)/cos x=sqrt3


Now what?
 
I think I got it:

(sin x+1)/cos x=sqrt3

square both sides:

(sin X+1)^2/Cos^2 x=(sqrt3)^2
(sin^2 x + 2sin x + 1)/(1-sin^2 x) =3
(sin^2 x + 2sin x + 1)=3(1-sin^2 x)
(sin^2 x + 2sin x + 1)= 3-3sin^2 x
4sin^2 x + 2sin x -2=0
(2sin x-1)(sin x +1)=0
sin x=1/2 & sin x=-1
x=pie/6 & x=3pie/2

Is this correct? Someone help please!!
 
Nice try, but did you check your answers?

"Squaring" things is a dangerous business.
 
Hello, flakine!

Use the same technique for the first one . . .

We have: .\(\displaystyle \tan x\,+\,\sec x\:=\:\sqrt{3}\)

Then: .\(\displaystyle \sec x\:=\:\sqrt{3}\,-\,\tan x\)

Square: .\(\displaystyle \sec^2x\:=\:3\,-\,2\sqrt{3}\cdot\tan x\,+\,\tan^2x\)

. . \(\displaystyle \tan^2x\,+\,1\:=\:3\,-\,2\sqrt{3}\cdot\tan x\,+\,\tan^2x\)

which simplifies to: .\(\displaystyle 2\sqrt{3}\cdot\tan x\:=\:2\;\;\Rightarrow\;\;\tan x\,=\,\frac{1}{\sqrt{3}}\;\;\Rightarrow\;\;x\,=\,\frac{\pi}{6},\,\frac{7\pi}{6}\)

And, as tkhunny cautioned, check these answers.
 
Top