# Angle between circle and tangent

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• July 11th 2011, 04:07 AM
RVMath
Angle between circle and tangent
Dear Forum members,

Attachment 21815
If radius R of the circle and the tangent length L are known, how could we calculate the angle (Theta) between the circle and the tanget?

Thank you very much for the help!

best regards

Raj
• July 11th 2011, 05:12 AM
kalyanram
Re: Angle between circle and tangent
Hi Raj,

There is an error in the figure you have attached the reference of $\theta$ as represented by an arc is a mistake it complicates things. I have modified the figure I hope this is what you intended to ask.

In the figure attached the angle suptended at the circumference is $\theta$ (by alternate segment theorem). So we have $\theta$ = $sin^{-1}(\frac{L}{R})$

Kalyan.