In the figure, θ1+θ2=2π and 3(BE)=4(AB). If the area of △CAB is 23−3 unit 2, when θ1θ2 is the largest, then the perimeter (in unit) of △CED is equal to _________.
Answer: 1
Solution
We have, θ1+θ2=2π and 3(BE)=4AB Let AB=x unit AC=xtanθ1ED=xtanθ2BE=BD+DE⇒34x=x(tanθ1+tanθ2)[∵3BE=4AB]⇒34=tanθ1+tan(2π−θ1)[∵θ1+θ2=2π]⇒tanθ1+cotθ1=34=3+31⇒tanθ1=3 or θ1=3π and θ2=6πorθ1=6π and θ2=3π∵θ1θ2 is largest ∴θ1=6π and θ2=3π Area of △CAB=21×x×xtanθ1⇒2x2tanθ1=23−3⇒x2=tan6π2(23−3)=12−63⇒x=3−3 Also, CE=x2+x2tan23π=(3−3)×2=6−23 Perimeter of △CED=CD+DE+CE=(3−3)+(3−3)tan3π+6−23=3−3+33−3+6−23=6