Question-69092

Question Number 69092 by Mr. K last updated on 19/Sep/19

Answered by mr W last updated on 21/Sep/19

Commented by mr W last updated on 21/Sep/19

AX=(a/(cos θ)) XY=((a−a tan θ)/(cos θ)) AX−XY=((a tan θ)/(cos θ))=((a sin θ)/(cos^2 θ)) (√(AX^2 +(AX−XY)^2 ))=(√((a^2 /(cos^2 θ))+((a^2 sin^2 θ)/(cos^4 θ)))) =(√((a^2 (cos^2 θ+sin^2 θ))/(cos^4 θ)))=(a/(cos^2 θ)) ((AX^2 )/( (√(AX^2 +(AX−XY)^2 ))))=((((a/(cos θ)))^2 )/(a/(cos^2 θ)))=a ⇒proved!

$${AX}=\frac{{a}}{\mathrm{cos}\:\theta} \\ $$$${XY}=\frac{{a}−{a}\:\mathrm{tan}\:\theta}{\mathrm{cos}\:\theta} \\ $$$${AX}−{XY}=\frac{{a}\:\mathrm{tan}\:\theta}{\mathrm{cos}\:\theta}=\frac{{a}\:\mathrm{sin}\:\theta}{\mathrm{cos}^{\mathrm{2}} \:\theta} \\ $$$$\sqrt{{AX}^{\mathrm{2}} +\left({AX}−{XY}\right)^{\mathrm{2}} }=\sqrt{\frac{{a}^{\mathrm{2}} }{\mathrm{cos}^{\mathrm{2}} \:\theta}+\frac{{a}^{\mathrm{2}} \mathrm{sin}^{\mathrm{2}} \:\theta}{\mathrm{cos}^{\mathrm{4}} \:\theta}} \\ $$$$=\sqrt{\frac{{a}^{\mathrm{2}} \left(\mathrm{cos}^{\mathrm{2}} \:\theta+\mathrm{sin}^{\mathrm{2}} \:\theta\right)}{\mathrm{cos}^{\mathrm{4}} \:\theta}}=\frac{{a}}{\mathrm{cos}^{\mathrm{2}} \:\theta} \\ $$$$\frac{{AX}^{\mathrm{2}} }{\:\sqrt{{AX}^{\mathrm{2}} +\left({AX}−{XY}\right)^{\mathrm{2}} }}=\frac{\left(\frac{{a}}{\mathrm{cos}\:\theta}\right)^{\mathrm{2}} }{\frac{{a}}{\mathrm{cos}^{\mathrm{2}} \:\theta}}={a} \\ $$$$\Rightarrow{proved}! \\ $$

Commented by TawaTawa last updated on 21/Sep/19