Polygon angular closure

$($a$)$ is an aid in determining if any blunder exists in zenith angle measurements

$($b$)$ should be less than the least count $($smallest horizontal circle graduation$)$ of your instrument

$($c$)$ can be determined even if some exterior and some interior angles are measured

$($d$)$ should be independent of your lengths of sights

An azimuth of $156-12-18$ has a corresponding back bearing of

$($a$)N23-47-42W$

$($b$)$ S $23-47-42$ E

$($c$)$ N $66-12-18$ E

$($d$)336-12-18$

The error in horizontal tape length due to sag can be minimized best by

$($a$)$ using a cloth instead of a steel tape

$($b$)$ using a calibration length based on a tape with ends held above the ground

$($c$)$ warming up the tape prior to its use

$($d$)$ balancing backsight and foresight distances

The bearing from $B$ to $A$ is $N11-19-21E$ and horizontal angle $A-B-C$ is $190-11-32.$ The bearing from $B$

to C is

$($a$)201-30-53$

$($b$)$ W $68-29-07$ S

$($c$)S21-30-53W$

$($d$)$ N $21-30-53$ E