# Find the exact value

1. Jun 26, 2008

### jimen113

1. The problem statement, all variables and given/known data
Find the exact value of the function:
tan(cos^-1 0.5)

2. Relevant equations

I used this formula: y=sin^-1=sin y=x for the first part, how do I solve the second part of the problem tanx (x)?

3. The attempt at a solution
x=cos^-1 (0.5)
cos(N)=0.5
N= pi/3
Then I tried tanx(x)=
I'm stuck

2. Jun 26, 2008

### D H

Staff Emeritus
Why did you change x to N?

3. Jun 26, 2008

### rocomath

$$\tan{(\cos^{-1}\frac 1 2)}=\tan x$$

$$x=\cos^{-1}\frac 1 2$$

$$x=\frac{\pi}{3}$$

Ok, you have x? So your equation just ... $$\tan x$$ ... solve for tangent!

4. Jun 26, 2008

### jimen113

Don't know? good question, but I see that I just have to plug in pi/3 into tanx (x)

5. Jun 27, 2008

### HallsofIvy

Staff Emeritus
[tex]tan(x)= tan(\pi/3)= \frac{sin(\pi/3)}{cos(\pi/3)}[/itex]
Surely you know $sin(\pi/3)$ and $cos(\pi/3)$!

Last edited: Jun 27, 2008
6. Jun 27, 2008

### dirk_mec1

The first line of ivy should be:
[tex]tan(x)= tan(\pi/3)= \frac{sin(\pi/3)}{cos(\pi/3)}[/itex]

7. Jun 27, 2008

### Dick

There's another way to do this. Draw a right triangle that has a angle of cos^(-1)(1/2) in it. E.g. hypotenuse 1 and adjacent side 1/2. Use Pythagoras to find the missing side. Now find tan by opposite/adjacent.

8. Jun 27, 2008

Thank you!