# trigonometry

posted by .

these two are the same type of questions but i have no clue how to figure out the answer. i have tried drawing it out but don't know what to do after that.
1. a bicycle with a 28-inch wheel(diameter) travels a distance of 800 feet. how many revolutions does the wheel make (to the nearest revolution)?

2. A wheel with a 20-inch radius is marked at two points on the rim. the distance between the marks along the wheel is found to be 3 inches. what is the angle (to the nearest tenth of a degree) between the radii to the two marks?
it would be realy helpful if you could explain to me how to figure out these two. thks

• trigonometry -

1. How far does the wheel go in 1 rotation?
C = piD = pi(28)inches
but 800 feet = 9600 inches
so no of rotations = 9600/(28pi) = 109 to the nearest whole number

for 2. is the 3 inches the straight line distance betweeen the points or is it measured along the arc?

If straight, use the Cosine Law,
If arc length, set up a ratio..
angle/360 = 3/(40pi), solve for "angle"