The sides of a triangle are a , b , and c and the angles opposite to them are A , B , and C , respectively. Given a = 3 , b = 8 , and sin A = 1 3 5 , what is the number of triangles that can be formed from the given data?
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We are given that a = 3 , b = 8 , and sin A = 1 3 5 so considering the possibility of triangle A B C being a right triangle, we see that 1 3 5 = c 3 , because sin A = Hypotenuse Opposite(A) , where c is the length of the hypotenuse of such a triangle. This leaves us with 3 9 5 = c 1 ⟹ c = 5 3 9 ⟹ c < 8 .
For any triangle A B C , such that a = 3 and sin A = 1 3 5 , the maximum possible length of any side of such a triangle should be 5 3 9 . Here, we have a side of length 8 which is larger than this maximal value hence, there are no triangles that can be formed from this data.
Shortest value ' a' can have is the perpendicular from B to AC .
The length of the perpendicular =b * Sin A =3.08.
But a=3<3.08.
So the triangle is not possible.
I used law of cosin and found the side opposite angle A to be approximatly 10.83. Then i used law of sin and found the two other angles. Logically the longest side should be opposite the largest angle and that didn't happen. Thus 0 triangles. This required use of calculator so not best solution.
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Relevant wiki: Sine Rule (Law of Sines)
Using the sine rule sin A a = sin B b = sin C c = 2 R we get 1 3 5 3 = sin B 8 sin B = 3 9 4 0 ⇒ sin B > 1 As we know that the maximum value of s i n B can be 1, hence this triangle is not possible.