1.define phase shift. could every sine function be expressed as a phase shifted cosine function? explain.

A phase shift is defined as the amount of x by which sinusoid is shifted to the left or right.
 
And yes, every sine function be expressed as a phase shifted cosine function:

sin(t)=cos(90-t)

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Distance=slopeslope is -2/4which equals-1/2the distance between these two points is -1/2