Mathematics (15 points)

1. By cos law,
cos2.54 = ( 6^2 + 6.13^2 + AB^2 )/(2)(6)(6.13)
AB = 0.26208
average speed = 0.26208/1 = 0.26208m/s = (0.26208/1000)/(1/3600) = 0.943km/h

2a angleOAC = 27
In tri OAC, tan27 = 250/AC
AC = 491m
b. angleOBC = 20
In tri OBC, tan20 = 250/BC
BC = 687m
c. angleBAC = 90
BC^2 - AC^2 = AB^2
686.870^2 - 490.652^2 = AB^2
AB = 481m