PreCal Sine and Cosine

[zman0825]

Find the exact value of cos 315° using the unit circle


Find the exact value of tan 135° using the unit circle

 

[Deleted member 4993]

Find the exact value of cos 315° using the unit circle


Find the exact value of tan 135° using the unit circle

Have you studied unit circle? In which quadrant does 315° fall?

Please show us your work, indicating exactly where you are stuck - so that we know where to begin to help you.

 

[zman0825]

i mean a little bit and 315 would be in quadrant 4 but that's about all that i get.............

 

[fasteddie65]

values of trig functions

135° is in Quadrant II, and has a reference angle of 45°. (180° - 135° = 45°) Since tangent is negative in Q II, tan 135° = - tan 45°. Now do you see?

315° is in Quadrant IV, and has a reference angle of 45° also. (360° - 315° = 45°) Since cosine is positive in Q IV, cos 315° = cos 45°. OK?

 

[zman0825]

Thanks i really appreaciate it.

 

[galactus]

Just look it up on the circle.

 

[Deleted member 4993]

For a quick review - go to:

http://www.youtube.com/watch?v=cIVpemcoAlY&NR=1

and

http://www.youtube.com/watch?v=ZffZvSH285c

and

http://en.wikipedia.org/wiki/Trigonometric_function