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Two birds X and Y on the ground and on the same side of a tree (T) tree at an angle of elevation of 45° and 60° respectively. If the dista 6m: (a) illustrate the information in a diagram; (b) calculate, correct to four significant figures, the height of the t

Mathematics

ScanSolve AI Answer

Answer

b

14.20 m14.20 \text{ m}

Step-by-step solution

4 steps

The problem states that two birds, X and Y, are on the ground and on the same side of a tree (T). The angles of elevation to the top of the tree from X and Y are 45∘45^\circ and 60∘60^\circ respectively. The distance between the birds X and Y is 6 m6 \text{ m}.

Part a

Illustrate the information in a diagram.

Let hh be the height of the tree.
Let T′T' be the top of the tree and TT be the base of the tree.
Let XX and YY be the positions of the birds on the ground.
Since the angle of elevation from Y (60∘60^\circ) is greater than from X (45∘45^\circ), bird Y is closer to the tree than bird X.
The distance between X and Y is 6 m6 \text{ m}.
Let dYd_Y be the horizontal distance from bird Y to the base of the tree.
Let dXd_X be the horizontal distance from bird X to the base of the tree.
Then dX=dY+6d_X = d_Y + 6.

\begin{tikzpicture} % Tree \draw[thick] (0,0) node[below] {$T$} -- (0,5) node[above] {$T'$}; \draw[dashed] (0,5) -- (5,0); % Line of sight from X \draw[dashed] (0,5) -- (2.88675,0); % Line of sight from Y % Ground \draw[thick] (-0.5,0) -- (6,0) node[right] {Ground}; % Bird Y \coordinate (Y) at (2.88675,0); \node at (Y) [below] {$Y$}; \pic[draw, angle radius=0.7cm, "$\theta_Y = 60^\circ$"] {angle = Y--0--5}; \draw (0,0) -- (Y); \node at (1.44, -0.5) {$d_Y$}; % Bird X \coordinate (X) at (5.88675,0); \node at (X) [below] {$X$}; \pic[draw, angle radius=1cm, "$\theta_X = 45^\circ$"] {angle = X--0--5}; \draw (Y) -- (X); \node at (4.38, -0.5) {$6 \text{ m}$}; % Height of tree \node at (-0.5, 2.5) {$h$}; % Right angle \draw (0,0.5) -- (0.5,0.5) -- (0.5,0); \end{tikzpicture}

Part b

14.20 m14.20 \text{ m}

Calculate, correct to four significant figures, the height of the tree.

  1. Set up trigonometric equations for both angles of elevation.

    From the diagram, we have two right-angled triangles.
    For bird Y:

    tan⁡(60∘)=hdY\tan(60^\circ) = \frac{h}{d_Y} dY=htan⁡(60∘)d_Y = \frac{h}{\tan(60^\circ)}

    For bird X:

    tan⁡(45∘)=hdX\tan(45^\circ) = \frac{h}{d_X} dX=htan⁡(45∘)d_X = \frac{h}{\tan(45^\circ)}
  2. Use the given distance between the birds to relate dXd_X and dYd_Y.

    We know that dX=dY+6d_X = d_Y + 6.
    Substitute the expressions for dXd_X and dYd_Y from Step 1:

    htan⁡(45∘)=htan⁡(60∘)+6\frac{h}{\tan(45^\circ)} = \frac{h}{\tan(60^\circ)} + 6
  3. Substitute the known values of tan⁡(45∘)\tan(45^\circ) and tan⁡(60∘)\tan(60^\circ) and solve for hh.

    We know tan⁡(45∘)=1\tan(45^\circ) = 1 and tan⁡(60∘)=3\tan(60^\circ) = \sqrt{3}.

    h1=h3+6\frac{h}{1} = \frac{h}{\sqrt{3}} + 6 h−h3=6h - \frac{h}{\sqrt{3}} = 6

    Factor out hh:

    h(1−13)=6h \left(1 - \frac{1}{\sqrt{3}}\right) = 6 h(3−13)=6h \left(\frac{\sqrt{3}-1}{\sqrt{3}}\right) = 6 h=633−1h = \frac{6\sqrt{3}}{\sqrt{3}-1}

    To rationalize the denominator, multiply the numerator and denominator by the conjugate of the denominator, (3+1)(\sqrt{3}+1):

    h=63(3+1)(3−1)(3+1)h = \frac{6\sqrt{3}(\sqrt{3}+1)}{(\sqrt{3}-1)(\sqrt{3}+1)} h=6(3⋅3+3⋅1)(3)2−(1)2h = \frac{6(\sqrt{3} \cdot \sqrt{3} + \sqrt{3} \cdot 1)}{(\sqrt{3})^2 - (1)^2} h=6(3+3)3−1h = \frac{6(3 + \sqrt{3})}{3 - 1} h=6(3+3)2h = \frac{6(3 + \sqrt{3})}{2} h=3(3+3)h = 3(3 + \sqrt{3}) h=9+33h = 9 + 3\sqrt{3}
  4. Calculate the numerical value and round to four significant figures.

    Using 3≈1.7320508\sqrt{3} \approx 1.7320508:

    h=9+3(1.7320508)h = 9 + 3(1.7320508) h=9+5.1961524h = 9 + 5.1961524 h=14.1961524 mh = 14.1961524 \text{ m}

    Rounding to four significant figures:

    h≈14.20 mh \approx 14.20 \text{ m}

    The height of the tree is 14.20 m\boxed{14.20 \text{ m}}.

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