How to Use the Law of Sines to Find the Missing Side of a Triangle: What is Side b?

To find the missing side of a triangle using the Law of Sines, we need to understand the relationship between the sides and angles of a triangle. The Law of Sines states that the ratio of the length of a side of a triangle to the sine of the angle opposite that side is constant for all three sides and angles of the triangle.

The formula is as follows:

a / sin(A) = b / sin(B) = c / sin(C)

Here, a, b, and c are the lengths of the sides opposite to angles A, B, and C respectively.

To find side b, you would rearrange the formula:

b = a * (sin(B) / sin(A))

Let’s assume we have the following values:

  • Side a = 10 units
  • Angle A = 30 degrees
  • Angle B = 45 degrees

First, we need to calculate the sine of the angles:

  • sin(A) = sin(30 degrees) = 0.5
  • sin(B) = sin(45 degrees) = √2/2 ≈ 0.707

Now plug these values into the formula to find b:

b = 10 * (0.707 / 0.5) = 10 * 1.414 = 14.14 units

Thus, the length of side b is approximately 14.14 units. This approach using the Law of Sines is ideal when you have at least one side and two angles of a triangle.

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