We can use The Law of Sines first to find angle C:
sinCAB=sinABC,
sinC12.2=314.5⋅2,C=arcsin145613.
The other angle C might be
180°−arcsin145613≈133.23°,but this is impossible, since the sum of the angles A and C is more than 180°.
Use "the three angles add to 180°" to find angle B:
B=180°−A−C=120°−C.
Now we can use The Law of Sines again to find AC:
sinBAC=sinABC,
sinB=sin(120°−C)=sin120°cosC−cos120°sinC=231−(145613)2−(−21)⋅145613=2903(9862+61),
AC=314.5⋅2sinB=101(9862+61).Answer:
C=arcsin145613≈46.77°,B=120°−C≈73.23°,AC=101(9862+61)≈16.03.
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