The given slopes are the tangent values of corresponding angles. Thus we have tan(a) =for one angle, "a", and tan(b) = for the other angle, "b". They ask you about . Using well known formulas of Trigonometry, = = = = = = = . The last step is to use the formula for tan(c/2) via tan(c) = . When you apply it, you will get the ANSWER = = = = = . According to the condition, you may use the sign " + " at sqrt instead of " +/- ". ANSWER. The slope is .