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HW 3-2
Precalculus
Law Sines & Cosines & Applications
Name: ___________________________
Law of Sines formula:
A. Putting it all together….
We use Law of Sines when we are given………
Law of Cosines formulas (standard and
angle forms):
When do you have to check for possible triangles?????
When do you use Law of Cosines??
B. Solve the triangle. Round sides to the nearest tenth and angles to the nearest whole degree.
Identify which of the four cases (SSA, AAS, SSS, SAS). If using the Law of Sines, is it acute
or obtuse? Compare h, a, and b. How many triangles? Watch out for no triangles or two
triangles!!!
1. A = 140  , b = 12, c = 14
2. a = 7.2, b = 6.5, c = 11
3. A = 126  , a = 18 , b = 13
4.
5. a = 15, b = 25, A = 47 
6. a = 18, b = 24, A = 45 
7. a = 6, b = 12, c = 16
8. b = 24.1, a = 10.5, A = 26.3 
C. Applications
9. A forest fire is spotted from two fire towers. The
triangle determined by the two towers and the fire has
angles of 28  and 37  at the tower vertices. If the
towers are 3000 meters apart, which one is closer to
the fire?
11. A triangular lot has sides measuring 120 meters,
186 meters and 147 meters. Find the measure of the
smallest angle.
10. One diagonal of a parallelogram is 5 centimeters
long, and the other is 13 cm long. They form an angle
of 42  with each other. How long are the sides of the
parallelogram? Hint: what do you know about the
diagonals of a parallelogram….