how can we find sin,cos,tan values like sin480, tan270?

Answer 1

reduce them by 360 until the values are between 0 and 360. So,

sin 480° = sin(480-360) = sin 120°

Now, you have to consider which quadrant you are in.

sin 120° = sin(180-120) = sin 60° = √3/2

sin 270° = sin(-90°) = -sin(90°) = -1

Now review this section in your text, and see how it all fits together.