Question 1030224
Hi there,
Your problem is best explained
as a triangle ABC
The two roads diverging at 
an angle of 75 degrees are
AB and AC.
The angle at A is 75 degrees
AB = car travelling at 56 mi/hr
after half an hour AB = 28 miles
AC = car travelling at 36 mi/hr
after half an hour AC = 18 miles
Using Cosine rule.
BC^2 = AB^2 + AC^2 - 2 x AB x AC x Cos(75)
BC^2 = 28^2 + 18^2 - (2 x 28 x 18 x Cos(75))
BC = √847.11
BC = 29.11 miles  (2 decimal places)
Cars are 29.11 miles apart.
Hope this helps :-)