Trigonometry help!(solved)

[Chanman]

I need help to answer this question:
Create a cosine equation with the following properties:
A max value of 6 when x=7π/16
A min value of -2 when x=5π/16

 

[Noah121]

I assume that by "cosine equation," you mean that it should be of the following form:

y = A cos(Bx+C) + D

for constants A,B,C,D that must be determined?

We know these:
(a) -1<=cos(x)<=1 for all x.
(b) cos(0) = 1, cos(pi) = -1, cos(pi/2)=cos(3 pi/2)=0, and that -1<=cos(x)<=1.

From Fact (a), you should be able to determine A and D. From Fact (b), you should be able to determine B and C.

 

[Chanman]

got it, thanks !