find the exact value of each trigonometric function of tan 180 degrees

Tan  = sin / cos    at 180 degrees =  0 /(-1) = 0

I think you must mean the value of each trig function of 180°

Note that  at 180°   x = -1, y = 0  and r = 1

So

sin (180)   =  y /r  =  0 /1  =  0

cos(180) = x / r =  -1 /1   = -1

sec (180)  = r /x = 1/-1  = -1

tan (180)  = y /x  =  0/ -1 = 0

Note that the csc and cot  are undefined because they are the reciprocals of sin and tan.....and each of these would result in a division by 0