I did that too! How many marks do you think would be awarded for that method ?
If you got 71.2 degrees, you'd probably lose 2-3 marks for not identifying the correct angle, however you would get a mark or 2 for working out the length of sides and using the tan rule
I saw on the instructions now that gel inks are not allowed, but any way nobody is going to notice it and it will be scanned (hopefully it will appear on the scanner) which is black and white.