Scope viewing angle calculation to field of view measurement

[Ray B]

It's been about 50 years since I used a Sine table but I am trying to compare fields of view of various scopes. Some scopes list the field of view in degrees of angle while others list them as linear feet/meters at a specific distance.
EXAMPLES:
Scope A is listed at 12.9 degrees
Scope B is listed at 43.8 feet @ 100 yards
As noted, with a book of trig functions I could input the angle, the distance and the coefficient and get the FOV in feet- but it's been a long time.
Can someone give the answer as to what a degree of exit results in feet at 100 yard/meters? Seems like it's a similar calculation to figuring out group size in MOA, but with bigger numbers.

 

[Nevada Smith]

The tangent function (tan) is the ratio of the opposite leg (side) to the adjacent leg (side). In other words, the ratio of the rise to the run (i.e., slope):

tan(1) degree is 0.01745506

0.01745506 X 100 yards (the length of the adjacent leg) = 1.745506 yards or 5.24 feet.

E.g.: Scope A is listed at 12.9 degrees or: 12.9 degrees X 5.24 feet @ 100 yards/degree = 67.6 feet @ 100 yards

 

[Ray B]

Great!! thanks so much. The nearest I could come was using Minute of Angle (1/60th degree) equaling about 1 inch at 100 yards, and I got the result 64.5 feet- the error being due to the slight error in 1 inch being multiplied by nearly 800 times. I'll need to write the tan 1 degree down- or better yet, dig through some old math books that show the various functions. Thanks again!!

 

[Nevada Smith]

Since I was in high school, I've been proficient in maths, e.g.:

 

[Country]

This going to be epic, Don't mind me.
Just here to tag in an learn.

 

[Ray B]

The quick answer is 5. Or, via Pythag... it's sq rt 3x3 + 4x4; ie sq rt 9+16, sq rt 25 = 5.