Back azimuth is related to the forward azimuth by which simple rule?

Back azimuth is related to the forward azimuth by which simple rule?

• A. Back azimuth is the forward azimuth plus 180 degrees or minus 180 degrees depending on the value
• B. Back azimuth is always equal to the forward azimuth
• C. Back azimuth is the forward azimuth minus 90 degrees
• D. Back azimuth is independent of the forward azimuth

Answer: (A)

The essential idea is that the back azimuth points in the exact opposite direction of the forward azimuth. Since azimuths are measured in degrees clockwise from north, the opposite direction is 180 degrees away. So you convert by adding 180 degrees, and if that pushes you past 360, you wrap around (subtract 360) to stay within 0–360. A practical way to think about it is: plus 180 degrees, or minus 180 degrees depending on the forward value. For example, a forward azimuth of 30° gives a back azimuth of 210°. A forward azimuth of 350° gives a back azimuth of 170°. This is why the simple rule described—back azimuth equals forward azimuth plus 180 degrees, with wrap-around as needed—is the correct one. The other options don’t fit because the back azimuth is not the same as the forward azimuth, not 90 degrees offset, and not independent of the forward direction; it is always the opposite direction, achieved by adding or subtracting 180 degrees.

The essential idea is that the back azimuth points in the exact opposite direction of the forward azimuth. Since azimuths are measured in degrees clockwise from north, the opposite direction is 180 degrees away. So you convert by adding 180 degrees, and if that pushes you past 360, you wrap around (subtract 360) to stay within 0–360. A practical way to think about it is: plus 180 degrees, or minus 180 degrees depending on the forward value.

For example, a forward azimuth of 30° gives a back azimuth of 210°. A forward azimuth of 350° gives a back azimuth of 170°. This is why the simple rule described—back azimuth equals forward azimuth plus 180 degrees, with wrap-around as needed—is the correct one.

The other options don’t fit because the back azimuth is not the same as the forward azimuth, not 90 degrees offset, and not independent of the forward direction; it is always the opposite direction, achieved by adding or subtracting 180 degrees.