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Evaluate x and y from the given figure.

Evaluate x and y from the given figure. Trigonometrical Ratios, R.S. Aggarwal Mathematics Solutions ICSE Class 9.

Trigonometrical Ratios

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Answer

In the given figure there are two right angled triangles, △ADC and △BDC.

In △ADC,

∠ACD = 60° and AC = 10 m, CD = x m

cos 60° = basehypotenuse\dfrac{\text{base}}{\text{hypotenuse}}

12=CDAC\dfrac{1}{2} = \dfrac{CD}{AC}

12=x10\dfrac{1}{2} = \dfrac{x}{10}

x = 5 m.

In △BDC,

BC = 525\sqrt{2} m

CD = x = 5 m

sin y° = perpendicularhypotenuse=DCBC=552=12\dfrac{\text{perpendicular}}{\text{hypotenuse}}= \dfrac{DC}{BC} = \dfrac{5}{5\sqrt{2}} = \dfrac{1}{\sqrt{2}}

sin y° = 12\dfrac{1}{\sqrt{2}}

sin y° = sin 45°

y° = 45°.

Hence, x = 5 m and y° = 45°.

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