I'm trying to get full marks but I'm only getting 2/4. My working is in blue.
BC = x and FC = x
find BF
x^2 + x^2 = bf^2
2 x^2 = bf^2
then bf^2 + x^2 = 20 ^2
2x^2 + x^2 = 400
3x^2 = 400
x = 11.547
+60 
