Looking at the table of John's times, he arrived at 8:42am and left at 5:14pm. If you are rounding to the nearest quarter hour, or 15 minutes, you time would need to be at the hour, 15 minutes after, 30 minutes after or 45 minutes after. Given those options, the closest times would be 8:45am and 5:15pm.
We know that sin²x+cos²x=1 so clear cos x cos x=(+/-)√[1-sin²x]
in this problem <span>Angle 0 is in quadrant 1 -----> cos o and sin o are positive </span>sin o=2/5 cos x=√[1-(2/5)²]----> cos o=√[1-4/25]----> cos o=√[21/25]---> cos o=√21/5
