KeerthanaPosted on Two observers are stationed due north of a tower (of height x metre) at a distance y metre from each other. The angles of elevation of the tower observed by them are 30° and 45° respectively. Then xyfrac{x}{y}yx is equal to a3−12frac{sqrt{3}-1}{2}23−1 b1 c2−12frac{sqrt{2}-1}{2}22−1 d3+12frac{sqrt{3}+1}{2}23+1 Answer : Option DExplanation : ∠PSQ=45∘,∠PRQ=30∘angle mathrm{PSQ}=45^{circ}, angle mathrm{PRQ}=30^{circ}∠PSQ=45∘,∠PRQ=30∘ From ΔPQS tan45∘=PQQS an 45^{circ}=frac{mathrm{PQ}}{mathrm{QS}}tan45∘=QSPQ ⇒1=xQS⇒QS=xRightarrow 1=frac{x}{mathrm{QS}} Rightarrow mathrm{QS}=x⇒1=QSx⇒QS=x metre From ΔPQR, tan30∘=PQQR an 30^{circ}=frac{mathrm{PQ}}{mathrm{QR}}tan30∘=QRPQ ⇒13=xx+yRightarrow frac{1}{sqrt{3}}=frac{x}{x+y}⇒31=x+yx ⇒3x=x+yRightarrow sqrt{3} x=x+y⇒3x=x+y ⇒3x−x=yRightarrow sqrt{3} x-x=y⇒3x−x=y ⇒x(3−1)=yRightarrow x(sqrt{3}-1)=y⇒x(3−1)=y ⇒xy=13−1=3+1(3−1)(3+1)Rightarrow frac{x}{y}=frac{1}{sqrt{3}-1}=frac{sqrt{3}+1}{(sqrt{3}-1)(sqrt{3}+1)}⇒yx=3−11=(3−1)(3+1)3+1 =3+13−1=3+12=frac{sqrt{3}+1}{3-1}=frac{sqrt{3}+1}{2}=3−13+1=23+1 metre Rate This:NaN / 5 - 1 votesAdd comment