Horizontal Curve Problem

[John QPE]

R = 1000'

Delta Angle = 16*38'

I'll leave out the rest of the problem as it's not relevant (I don't think it is)

So ... this problem was a basic HC problem, with several questions .. Find T, BC, EC, LC, L, E, M

So I solve for E and get 10.62 ft which was correct.

The next question is solve for M ...

So since E is still in my calculator I use M= E cos(Delta/2) which equals 10.18 ... not an answer choice.

I then use M = R(1-cos (Delta/2)) which equals 10.52 .... which is an option (and the correct one I might add)

So what gives? Is there a rule of thumb for these equations that I don't know about??

I'll make up a full HC problem tomorrow for the board.

Thanks

 

[civilized_naah]

There's nothing wrong with the equations. You forgot to divide the angle by 2 when you used E=10.62 to calculate M directly. Instead of using angle = 8.32, you used 16.64

 

[John QPE]

That's embarrassing :Failed:

Thanks Dr. G

 

[civilized_naah]

No problem. Better these kinks get worked out before the test than during.