SOLUTION: I have two questions. 1. Find the area of triangle ABC if A=56 degrees, b=20 ft, and c=12 ft. Round to the nearest tenth. 2. In triangle ABC, A=35 degrees, a=43 and c=20. Det

Algebra ->  Trigonometry-basics -> SOLUTION: I have two questions. 1. Find the area of triangle ABC if A=56 degrees, b=20 ft, and c=12 ft. Round to the nearest tenth. 2. In triangle ABC, A=35 degrees, a=43 and c=20. Det      Log On


   



Question 172762: I have two questions.
1. Find the area of triangle ABC if A=56 degrees, b=20 ft, and c=12 ft. Round to the nearest tenth.
2. In triangle ABC, A=35 degrees, a=43 and c=20. Determine whether triangle ABC has no solution, one solution, or two solutions. Then solve the triangle. Round to the nearest tenth.
I must show all my work, and I'm not really sure how to do either problem.
thanks

Found 2 solutions by Alan3354, jojo14344:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
1. Find the area of triangle ABC if A=56 degrees, b=20 ft, and c=12 ft. Round to the nearest tenth.
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If you sketch it, then draw the altitude from the end of b, that altitude = 10*sin(56) and it's the h of A = bh/2.
Area = 12*20*sin(56)/2
Area = 99.5 sq units
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2. In triangle ABC, A=35 degrees, a=43 and c=20. Determine whether triangle ABC has no solution, one solution, or two solutions. Then solve the triangle. Round to the nearest tenth.
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Use the Law of Sines
a/sin(A) = c/sin(C)
43/sin(35) = 20/sin(C)
sin(C) = 20*sin(35)/43 = 0.26677974
C = 15.4727 degs or 164.5273 degs (from inverse sine)
C cannot be 164... degs, tho, because adding A would exceed 180 degs.
So C = 15.4727 degs, and there is only one solution.
Angle B = 180 - (A+C) = 129.5273 degs
side b/sin(B) = a/sin(A)
b = 43*sin(B)/sin(A)
b = 57.825

Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!
We know the Area of a Triangle: A%5BT%5D=%281%2F2%29bh
1) let's see the triangle with given dimensions:

Simply by Trigo function: we can get d=height:
sin56%5Eo=opp%2Fhyp=d%2F12
d=%28sin56%5Eo%29%2812%29=9.95ft
Therefore:
A=%281%2F2%29bh=%281%2F2%29%2820%29%289.95%29
highlight%28A=99.5ft%5E2%29, Answer
.
2)In triangle ABC, A=35 degrees, a=43 and c=20. Then solve the triangle.
I guess you're just finding the dimensions of the this triangle?
Okay, we'll see 1st the triangle:

same thing, by trigo Function we solve for d:
Sin35%5Eo=d%2F20
d=%28sin35%5Eo%29%2820%29=11.47ft
For Angle C:
sinC=d%2Fa --->C=sin%5E%28-1%29%2811.47%2F43%29
C=15.47%5Eo
.
therefore, Angle B=180-A-C=180-35-15.47
B=129.53%5Eo
.
For side b, USE COSINE Law:
b%5E2=a%5E2%2Bc%5E2-2accosB
b%5E2=43%5E2%2B20%5E2-2%2843%29%2820%29cos129.53%5Eo
b=sqrt%283343.735%29
b=57.83ft
Thank you,
Jojo