SSC JE Civil Engineering 23-Mar-2021 Shift 1 Paper

Concept:
We know the relationship between FB and BB
Back bearing (BB) = Fore bearing (FB) ± 180°.
+ve sign is used if FB is less than 180° and –ve sign is used if FB is more than 180°.
Included angle = Fore Bearing of next line - Back Bearing of the previous line
Calculation: Fore Bearing of AB = 150°15'
Included Angle ABC = 110°30'
Back Bearing of AB = 150°15' + 180° = 330°15'
Included angle ABC $=\mathrm{F}.{\mathrm{B}}_{\mathrm{BC}}-\mathrm{B}.{\mathrm{B}}_{\mathrm{AB}}$
110°30' $=\mathrm{F}.{\mathrm{B}}_{\mathrm{BC}}$ - 330° 15'
$\mathrm{F}.{\mathrm{B}}_{\mathrm{BC}}$ = 440°45'
$\mathrm{F}.{\mathrm{B}}_{\mathrm{BC}}$ = 440°45' - 360° = 80° 45'
Note:
If the included angle is negative, then add 360°.
If the included angle is greater than 360° then deduct 360°.