There is a period for sine and cosine that is 2pi, it is 2pi because it is one revolution of the unit circle, it is how much times it takes to repeat its cycle. When we use A,S,T,C on out graph we know that Sine is positive n quadrant 1 and 2 and will be negative on 3,4 . now for cosine it is positive on quadrant 1 and 4 but will be negative on 2 and 3 . as you can see it takes 4 to repeat the pattern which is why it takes 2pi but with tangent it only takes pi because it is positive negative then positive and negative again so it repeats after the second one.
the fact that it has amplitudes it makes sine and cosine have restrictions. the restriction are 1 and -1 with this restrictions they cant go past a certain paint un like tangent. if we try any number it wont work because of the restriction so its the same like the unit circle.