Question : Let A and B be two towers with the same base. From the midpoint of the line joining their feet, the angles of elevation of the tops of a and b are 30o and 45o, respectively. The ratio of the heights of A and B is:
Option 1: $1: 3$
Option 2: $1: \sqrt{3}$
Option 3: $\sqrt{3}: 1$
Option 4: $3: 1$
Correct Answer: $1: \sqrt{3}$
Solution : In $\triangle ACE$, $\frac{AC}{CE} = \tan 30^{\circ}$ ⇒ $\frac{AC}{CE} = \frac{1}{\sqrt3}$ ⇒ $CE = \sqrt3 AC$ -------------(i) In $\triangle BDE$, $\frac{BD}{ED} = \tan 45^{\circ}$ ⇒ $\frac{BD}{ED} = 1$ ⇒ $ED = BD$ -------------(ii) Since CE = ED, ⇒ $\sqrt 3 AC = BD$ ⇒ $\frac{AC}{BD} = \frac{1}{\sqrt3}$ So, the ratio of heights = $1: \sqrt3$ Hence, the correct answer is $1: \sqrt3$.
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Question : Solve for $\theta: \cos ^2 \theta-\sin ^2 \theta=\frac{1}{2}, 0<\theta<90^{\circ}$.
Option 1: 45o
Option 2: 60o
Option 3: 30o
Option 4: 40o
Question : The total surface area of a regular triangular pyramid with each edge of length 1 cm is:
Option 1: $4 \sqrt{3}$ cm2
Option 2: $\frac{4}{3} \sqrt{3}$ cm2
Option 3: $\sqrt{3}$ cm2
Option 4: $4$ cm2
Question : The difference between the semi-perimeter and the sides of ΔPQR are 18 cm, 17 cm, and 25 cm, respectively. Find the area of the triangle.
Option 1: $330\sqrt{510}$ cm2
Option 2: $230\sqrt{510}$ cm2
Option 3: $30\sqrt{510}$ cm2
Option 4: $130\sqrt{510}$ cm2
Question : The sides $P Q$ and $P R$ of $\triangle P Q R$ are produced to points $S$ and $T$, respectively. The bisectors of $\angle S Q R$ and $\angle T R Q$ meet at $\mathrm{U}$. If $\angle \mathrm{QUR}=59^{\circ}$, then the measure of $\angle \mathrm{P}$ is:
Option 1: 31o
Option 2: 62o
Option 3: 41o
Option 4: 49o
Question : If the angle of elevation of the Sun changes from 30° to 45°, the length of the shadow of a pillar decreases by 20 metres. The height of the pillar is:
Option 1: $20(\sqrt{3}-1)$ m
Option 2: $20(\sqrt{3}+1)$ m
Option 3: $10(\sqrt{3}-1)$ m
Option 4: $10(\sqrt{3}+1)$ m
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