Question

PLEASE HELP
The function f(t) = 5 cos(pi over 4t) + 11 represents the tide in Dark Sea. It has a maximum of 16 feet when time (t) is 0 and a minimum of 6 feet. The sea repeats this cycle every 8 hours. After six hours, how high is the tide?

Answer 1

Ive typed it into my calculator several different ways but am unable to get any of these answers
A. 11 feet

B. 6 feet

C. 8.5 feet

D. 10.5 feet

Answer 2

I keep getting 15.9

Answer 3

@satellite73

Answer 4

@jim_thompson5910

Answer 5

@robtobey

Answer 6

Plug in t = 6 and evaluate.

f(t) = 5*cos((pi/4)*t) + 11

f(6) = 5*cos((pi/4)*6) + 11

f(6) = 5*cos(3pi/2) + 11

f(6) = 5*0 + 11 ... use the unit circle here

f(6) = 0 + 11

f(6) = 11

So at t = 6 hours, the height is 11 feet

Answer 7

Thanks so much omgg...