This one and this one are going to be obtuse so very simple idea if one line or if one ray is relative to the other one is straight up and down versus left to the right or is completely upright then we're talking about a right angle if they are closer to each other if you had to rotate them less you're talking about a acute angle if you had to rotate them more you are talking about an obtuse angle and I think if you look at them visually it's pretty easy to pick out