Question 442956
We know that angle A is opposite BC.

Let's call side AB and side AC

We can find what cos(A) is since we know A = 20º

Let's use the law of cosines.

Let BC = a, AB = c , AC = b

a^2 = b^2 + c^2 - 2bc cos(20)

a^2 = 12^2 + 6^2 - 2(12)(6)cos(20)

a^2 = 144 + 36 - (144cos(20)

a^2 = 180 - 144*cos(20º)

Use your calculator find cos(20º). Make sure your calculator is in DEGREE MODE and not RADIAN MODE.

a^2 = 180 - 144 * (0.939692621)
a^2 = 44.6842626
a = 6.68462883

We know that (1/2)(a)(b) gives us the area.

We have a and we have b.

(1/2)(6.68462883)(6) = 20.053888565 cm.

{{{20.1}}}cm when rounded.