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1 106. 在A點測得AB之磁方位角等於40°30'20",在C點測得CB之磁方位角等於290°10'40",則∠ A B C =
A 1 1 0 ° 1 9 ' 4 0 "
B 6 9 ° 4 0 ' 2 0 "
C 1 0 9 ° 3 9 ' 4 0 "
D 2 4 9 ° 4 0 ' 2 0 "