# Thread: Double angle formulas of seceant, cosecant, and cotangent

1. ## 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: $sec2\theta$). 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.

2. 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: $sec2\theta$). 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.
$sec 2x = \frac{1}{cos 2x}$

3. Ok thanks

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

Triangle lengths :
opposite = 3
hypotenuse = 5

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

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

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

4. Originally Posted by mathgeek777
Ok thanks

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

Triangle lengths :
opposite = 3
hypotenuse = 5

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

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

For $cot2\theta$ I got $\frac{7}{24}$
Looks fine to me

5. Originally Posted by janvdl
Looks fine to me