Since the angle is obtuse, we know that it has to be the largest angle. The opposite side of the largest angle in a triangle must be the hypotenuse. Using that logic, we can rule out sin and cos, and continue by using tangent. With this knowledge, we can take the tangent of an angle larger than 90* and we find that it is =~ -57 (91*) we can thus assume it’s either b. Or d. I lean more towards d. But choose either of those.
