Answer:
I'm not sure if this will be able to help, though I found the same question, but answered by someone who is far more advanced with this, and has answered for more questions than I have. Hope this can help, if not please comment, so I can delete.
brainly.com/question/21188240
I don't know you have to use a measuring tool to figure it out ruler helps sorry try a ruler of a angle scale
I m getting 308.11, there is an additional 0.60 that is added, maybe your source is wrong, or there is a copying error.