Concept:Use inverse trigonometric identities and known standard angle values.Explanation:We are given sin−121=tan−1x. Recall that sin30∘=21, so sin−121=30∘ (taking the principal value). Thus the equation becomes 30∘=tan−1x. Taking tan of both sides gives tan30∘=x. Since tan30∘=31, we obtain x=31.Answer:x=31; option B is correct.