Practicing Success
If \(\frac{sinx}{siny}\)=\(\frac{1}{2}\) and \(\frac{cosx}{cosy}\)=\(\frac{3}{2}\), then find the value of cot2x + sin2x. |
\(\frac{889}{162}\) \(\frac{889}{160}\) \(\frac{821}{225}\) 1 |
\(\frac{889}{160}\) |
⇒ \(\frac{sinx}{siny}\)=\(\frac{1}{2}\) ⇒ 2sinx = siny ....(1) ⇒ \(\frac{cosx}{cosy}\)=\(\frac{3}{2}\) ⇒ 2cosx = 3cosy ...(2) Squaring and Adding eq. (1) & (2) 4sin2x = sin2y 4cos2x = 9cos2y ⇒ 4sin2x + 4cos2x = sin2y + 9cos2y 4(sin2x + cos2x) = sin2y + 9cos2y 4 = sin2y + cos2y + 8cos2y [sin2θ + cos2θ = 1] 4 = 1 + 8cos2y 3 = 8cos2y \(\frac{3}{8}\) = cos2y cosy = \(\frac{\sqrt {3}}{\sqrt {8}}\) Now, if we divide both given equation we get: tanx . coty= \(\frac{1}{3}\) tanx × \(\frac{\sqrt {3}}{\sqrt {5}}\) = \(\frac{1}{3}\) tanx = \(\frac{\sqrt {5}}{3\sqrt {3}}\) = \(\frac{P}{B}\) H = \(\sqrt {(3\sqrt {3})^2 + (\sqrt {5})^2}\) H = 4\(\sqrt {2}\) Put in & find out: ⇒ cot2x + sin2x = (\(\frac{3\sqrt {3}}{\sqrt {5}}\))2 + (\(\frac{\sqrt {5}}{4\sqrt {2}}\))2 = \(\frac{889}{160}\) |