cot 390 degrees

**daydreembelievr** · November 5th 2008, 11:49 PM

find the exact value of 390 degrees.

can anyone help me figure out how to start this?thanks much

**mr fantastic** · November 6th 2008, 12:29 AM

Originally Posted by daydreembelievr

find the exact value of cot 390 degrees.

can anyone help me figure out how to start this?thanks much

I assume the red stuff was missing .....

cot (390 degrees) = cot(30 degrees).

**Reece** · November 6th 2008, 02:08 AM

cot(390)
= cot(30)
= cos(30)/sin(30)

**daydreembelievr** · November 6th 2008, 02:05 PM

why is it equal to cot 30 degrees? sorry if it is obvious.

Is it because 390 - 360 = 30
If so, it it -360 because 360 is a coterminal angle? thanks

**mr fantastic** · November 6th 2008, 04:36 PM

Originally Posted by daydreembelievr

why is it equal to cot 30 degrees? sorry if it is obvious.

Is it because 390 - 360 = 30
If so, it it -360 because 360 is a coterminal angle? thanks

Try showing 390 degrees on a unit circle. What do you notice?

Thread: cot 390 degrees