✔ 最佳答案
By sine law,
sinE/e = sinF/f
sin144°/10.5m = sinF/12.5m
sinF = (12.5/10.5)sin144°
sinF = (25/21)sin144°
sinF = 0.6997
F = 44.4065° or 135.5935°
For E = 144°, F = 44.4065°,
D = 180° - 144° - 44.4065°
D = -8.4064° (rejected as < 0)
For E = 144°, F = 44.4065°,
D = 180° - 144° - 135.5935°
D = -99.5935° (rejected as < 0)
So it's impossible for such situation and so no solution.
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Actually, for an angle more than 90°, it should have the longest length in the respective side. (e.g. angle E and side e). If the respective side of the angle more than 90° is not the longest, it's of no solution.
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By the way, the sine law is not applicable to an exterior angle.
For all the angles in the sine law,
sinA/a=sinB/b=sinC/c
0° < A < 180°, 0° < B < 180°, 0° < C < 180°
