9514 1404 393
Answer:
- BC = 24.0
- AC = 26.0
- m∠B = 73.4°
- m∠B = 30.0°
Explanation:
The law of sines tells you the ratio of sides is the same as the ratio of sines of their opposite angles.
This post has 2 kinds of problems.
1) 2 angles and the side between them are given.
2) 2 sides and the angle opposite the longest is given.
For the first type, you need to determine the missing angle (opposite the given side). That comes from the sum of angles of a triangle being 180°. Then you find the remaining sides using the ratio of sines.
For the second type, the angle opposite the shorter side is found using the ratio of sides to find the sine of that angle. Then the third side and third angle can be found using the ratio of sides to find the sine of the angle, and using the ratio of sines to find the missing side.
Straightforward, and tedious. For more than one, I like to use a spreadsheet to crunch the numbers.
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1) BC = 24.0
2) AC = 26.0
3) m∠B = 73.4°
4) m∠B = 30.0°
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In the spreadsheet, the given values are in the first 3 columns. The 4th column is the first one calculated. As indicated above, the angle calculation for problems 1 and 2 uses the sum of angles relation. For problems 1 and 2, this is the angle opposite the given side. The "first side" is the side opposite the "first angle". c = b·sin(C)/sin(B), for example.
For problems 3 and 4, the first unknown angle is the one opposite the "short side", which is the shorter of the given sides. As it happens, this is the side that is asked for in the question. B = arcsin(c·sin(B)/sin(C))
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Additional comment
In a spreadsheet, angles are presumed to be in radians for all of the trig functions. We use the DEGREES( ) and RADIANS( ) functions to convert as appropriate.