Answer:
a = 16.51
angle A = 54
angle B = 63
Explanation:
Recall the law of sines:
sinA/a = sinB/b = sinC/c
We know c is 20, and angle C is 63. Since b is also 20, angle B must also be 20. We know have two of the 3 angles, summing to 126, and we can find the last angle from that. 180-126=54, so angle A must be 54.
To solve for a, we need to know the ratio of the other two terms. Sin(63) is around 0.99, and 0.99/20 is 0.049. So we have 0.049=sin(54)/a. To solve for a, we divide by sin(54) and take the reciprocal of both sides, giving a = (sin54)/0.049, which is about 16.51, which is the length of the side a.