expand tan(x-a) and tan(x-b) using the tangent subtracting identity substitute it to the given equation (tan2x=tan(x-a)tan(x-b)) then simplify the numerator and denominator then the equation will become ... and then use the double angle formula for tangent tan2x=2tanx/1-tan2x and substitute into...
expand heron's formula in terms of a,b, and c simplifying it to involve sums like ab+bc+ca and a2+b2+c2 then apply the inequalities bound to A2 and take the root to bound A