Math Trig
posted by yeahyeah .
13. What is the equation of a cosine function with amplitude 3, transition point (−1, 1), and period p?
A. y = p cos [3(x − 1)] − 1
B. y = 3 cos [2(x − 1)] + 1
C. y = 3 cos [p (x + 1)] − 1
D. y = 3 cos [2(x + 1)] + 1
16. What is the transition point of y = 100 tan (6x) + 4?
A. (0, −4)
B. (6, −4)
C. (0, 4)
D. (6, 4)
20. cotâ€“1 −0.57735 is approximately
A. −1.05.
B. 2.09.
C. −0.65.
D. 2.62.

13.
amplitude 3: 3cos(...)
period p: 3cos(2pi(...)/p) ...
translate by (1,1): 3cos(2pi(x+1)/p) + 1
So, it appears to be (D), if by p you mean pi.
16: (0,4): (C)
20: (A)
Your use of transition point appears unusual. In #13 the only possible interpretation, given the answer choices, is to use (1,1) as coordinate translation. Yet transition points are usually max/min or inflection points. Using that same logic gives me (C) on #16.