Question : From an aeroplane just over of river, the angle of depression of two palm trees on the opposite bank of the river is found to be $60^{\circ}$ and $30^{\circ}$, respectively. If the breadth of the river is 400 metres, then the height of the aeroplane above the river at that instant is: $(\sqrt{3} = 1.732)$
Option 1: 173.2 metres
Option 2: 346.4 metres
Option 3: 519 .6 metres
Option 4: 692.8 metres
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Correct Answer: 173.2 metres
Solution : Let, $BC$ = River = $400$ m $AD$ = Height of plane = $H$ m $BD=x$ m $CD=(400-x)$ m From $\Delta ABD$, $\tan 60^{\circ} = \frac{AD}{BD}$ $⇒\sqrt3 = \frac{H}{x}$ $⇒H = \sqrt3x$ $⇒x=\frac{H}{\sqrt3}$--------------(i) From $\Delta ADC$, $\tan 30^{\circ} = \frac{AD}{CD}$ $⇒\frac{1}{\sqrt3} = \frac{H}{400-x}$ $⇒\sqrt3H = 400-x$ Putting the value of $x$ from equation (i), we get, $⇒\sqrt3H = 400-\frac{H}{\sqrt3}$ $⇒4H=400\sqrt3$ $⇒H= 100\sqrt3 $ $\therefore H=173.2$ [As $\sqrt3=1.732$] Hence, the correct answer is 173.2 metres.
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Question : A pilot in an aeroplane at an altitude of 200 metres observes two points lying on either side of a river. If the angles of depression of the two points be $45^{\circ}$ and $60^{\circ}$, then the width of the river is:
Option 1: $(200+\frac{200}{\sqrt{3}})$ metres
Option 2: $(200-\frac{200}{{\sqrt3}})$ metres
Option 3: $400 {\sqrt3}$ metres
Option 4: $(\frac{400}{{\sqrt3}})$ metres
Question : In $\triangle ABC, \angle B = 60^\circ$ and $\angle C = 40^\circ$, AD and AE are respectively the bisectors of $\angle A$ and perpendicular on BC. Find the measure of $\angle EAD$.
Option 1: $11^\circ$
Option 2: $10^\circ$
Option 3: $12^\circ$
Option 4: $9^\circ$
Question : In a triangle the length of the opposite side of the angle which measures 45° is 8 cm, what is the length of the side opposite to the angle which measures 90°?
Option 1: $8\sqrt{2}$ cm
Option 2: $4\sqrt{2}$ cm
Option 3: $8\sqrt{3}$ cm
Option 4: $4\sqrt{3}$ cm
Question : ABCD is a cyclic quadrilateral in which angle B is opposite to angle D. If $\angle \mathrm{B}=(\mathrm{x}+10)^{\circ}$ and $\angle \mathrm{D}=(2 \mathrm{x}+35)^{\circ}$, then what is the value of $\mathrm{x}$?
Option 1: 40$^{\circ}$
Option 2: 45$^{\circ}$
Option 3: 50$^{\circ}$
Option 4: 35$^{\circ}$
Question : Minor arc $BC$ subtends $\angle BAC$ and $\angle BDC$ at points $A$ and $D$, respectively, on the circumference of the major sector of the circle with centre $O$. What is the value (in degrees) of $(\angle ABC+\angle ACB)$, if $\angle BDC=73^{\circ}?$
Option 1: $117^{\circ}$
Option 2: $107^{\circ}$
Option 3: $103^{\circ}$
Option 4: $113^{\circ}$
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