# Double angle formulas of seceant, cosecant, and cotangent

• Jan 26th 2008, 10:33 AM
mathgeek777
Double angle formulas of seceant, cosecant, and cotangent
How do they differ from the sine, cosine, and tangent double angle formulas, if at all? I've been asked on homework to find the trigonometric function of (ex: $\displaystyle sec2\theta$). I know how to find it, I'm just not sure if there's a different double angle identity I have to use when using the inverse of cosine.
• Jan 26th 2008, 10:40 AM
janvdl
Quote:

Originally Posted by mathgeek777
How do they differ from the sine, cosine, and tangent double angle formulas, if at all? I've been asked on homework to find the trigonometric function of (ex: $\displaystyle sec2\theta$). I know how to find it, I'm just not sure if there's a different double angle identity I have to use when using the inverse of cosine.

$\displaystyle sec 2x = \frac{1}{cos 2x}$
• Jan 26th 2008, 10:48 AM
mathgeek777
Ok thanks :)

I'm gonna run some answers by you guys real quick

Triangle lengths :
opposite = 3
hypotenuse = 5

For $\displaystyle sec2\theta$ I got $\displaystyle \frac{25}{7}$

For $\displaystyle csc2\theta$ I got $\displaystyle \frac{25}{24}$

For $\displaystyle cot2\theta$ I got $\displaystyle \frac{7}{24}$
• Jan 26th 2008, 10:53 AM
janvdl
Quote:

Originally Posted by mathgeek777
Ok thanks :)

I'm gonna run some answers by you guys real quick

Triangle lengths :
opposite = 3
hypotenuse = 5

For $\displaystyle sec2\theta$ I got $\displaystyle \frac{25}{7}$

For $\displaystyle csc2\theta$ I got $\displaystyle \frac{25}{24}$

For $\displaystyle cot2\theta$ I got $\displaystyle \frac{7}{24}$

Looks fine to me ;)
• Jan 26th 2008, 10:54 AM
mathgeek777
Quote:

Originally Posted by janvdl
Looks fine to me ;)

Awesome! Thanks for your help (Handshake):)
• Jan 26th 2008, 10:55 AM
janvdl
Quote:

Originally Posted by mathgeek777
Awesome! Thanks for your help (Handshake):)

You're welcome (Handshake) :D