tan(pi/8)

• October 7th 2005, 12:52 AM
a4swe
tan(pi/8)
Anyone got any leads on solving:
$
tan(\frac{\pi}{8})
$
• October 7th 2005, 01:41 AM
ticbol
Solve? You mean looking it up on a calculator is not enough?
Anyway, my calculator here says tan(pi/8) = 0.414213562.

Or, maybe, you mean this, (one of many ways):
tan(pi/8) = tan[(pi/4)/2]
We know the trig functions value of pi/4 (or 45 degrees) without bothering to consult a clculator, so, maybe this is what you mean by "solve for tan(pi/8).

Okay. Then we know also this trig identity:
tan(A/2) = (1 -cosA)/sinA = sinA/(1 +cosA) ----***

If A = pi/4, then without calculator, we can solve for tan(A/2).

tan(pi/8)
= tan[(pi/4)/2]
= [1 -cos(pi/4)]/[sin(pi/4)]
= [ 1 -1/sqrt(2)]/[1/sqrt(2)]
= in the end, sqrt(2) -1
= 1.4142... -1
= 0.4142.....

Or,
tan(pi/8)
= [sin(pi/4)]/[1 +cos(pi/4)]
= sqrt(2) -1
= 0.4142....
• October 7th 2005, 02:01 AM
a4swe
Yep, like that. :)
Thanks.