Help with precalculus work

Question

(I was able to solve some of the equation. (Those answers are in bold.) I just need some help finishing the equation.)

There should be 4 solutions for B but I can only find 2 and I'm just completely confused on how to find the answer for C.

An airplane is asked to stay within a holding pattern near Chicago's O'Hare International Airport. The function d(x) = 75sin(0.65x) + 145 represents the distance, d, in miles, of the airplane from the airport at time ,, in minutes.

A) When the plane enters the holding pattern, x = 0 , how far is it from O'Hare?

When the plane enters the holding pattern, the plane is 145 miles.

B) During the first 20 minutes after the plane enters the holding pattern, at what time is the plane exactly 130 miles from the airport? Round to the nearest thousandth.

The time when the plane is exactly 130 miles from the airport are {5.143,9.356}

) During the first 20 minutes after the plane enters the holding pattern, at what time, z, is the plane more than 130 miles from the airport?

The plane is more than 130 miles from the airport during these intervals.....

Answer 1

sin.65x = 0

.65x = 0, pi, 2pi, 3pi

x = 0, pi/.65, 2pi/.65, 3pi/.65, ...

= 0, 4.83322, 9,66644, 14.49966 when it's 145 miles away

75sin.65x +145 = 130 miles

75sin.65x = 130-145 = -15

sin.65x = -15/75 = -1/5=-.2

.65x = the angle whose sign = -.2 = -.20136 or pi+.20136

x = -.20136/.65 = or (2pi-.201)/.65 = 9.357

or

x= 3.343/.65 = 5.143 minutes = exactly the same answer you have,

for more solutions, look for more cycles of the sine wave

if x is measured in radians. which is how you got 5.143

if x is measured in degrees, you get different answers

75sin.65x + 145 = 130

75sin.65x = -15

sin.65x = -15/75=-.2

.65x = the angle whose sine = -.2 = -11.537 or 180+11.537 = 191.537

x = 191.537/.65 = 294.672 minutes

or use a graphing calculator, on line or hand held type