Find the are of the triangle ABC in 3D

Calculate the area of the triangle ABC where A is (-1,2,4) B is (1, -1, 2), and C is (2, 3, 4)?

I am not sure where to start please show ur work.

Use Heron's formula. Calculate the lengths of the sides in the standard way,

then use the formula A = sqrt(s*(s - a)*(s - b)*(s - c)), where a, b and c are the

lengths of the sides and s = (1/2)*(a + b + c).

I get lengths of sqrt(17), sqrt(10) and sqrt(21), so that

s = (1/2)*(sqrt(10) + sqrt(17) + sqrt(21)). It would be easiest to convert these

values to decimal form and then make the necessary calculations.

I get a final answer of 6.345 square units to 3 decimal places.