Answer:
BC ≈ 21 units
Step-by-step explanation:
This problem cannot use the Pythagorean theorem as it is not a right triangle. However, you can use the law of cosines, which states that the formula [tex]c^2 = a^2 + b^2 -2abCos(c)[/tex] works for any triangle (given that a, b and c are sides of a triangle and the angle c is opposite vertices C)
In this case, a and b can be replaced with 12 and 15 respectively, and angle c is 105 degrees.
[tex]c^2 = 12^2 + 15^2 -2*12*15Cos(105)[/tex]
[tex]c^2 = 144 + 225 -360Cos(105)[/tex]
[tex]c^2 = 369 -360Cos(105)[/tex]
the cosine of 105 degrees is about -0.25882 rounded to the 5th decimal place
After the difference, you should end up with BC^2 and by taking its root, you should end up with about 21.49825 or rounded to the nearest whole number, 21.
Hope this helps : )
