AI Mentor

Check Your IQ

Free Expert Demo

Try Test

Courses

Dropper NEET Course Dropper JEE Course Class - 12 NEET Course Class - 12 JEE Course Class - 11 NEET Course Class - 11 JEE Course Class - 10 Foundation NEET Course Class - 10 Foundation JEE Course Class - 10 CBSE Course Class - 9 Foundation NEET Course Class - 9 Foundation JEE Course Class -9 CBSE Course Class - 8 CBSE Course Class - 7 CBSE Course Class - 6 CBSE Course

Offline Centres

A lamp post standing at a point A on a circular path of radius r subtends an angle α at some point B on the path, and AB subtends an angle of $45^{\circ}$ at any other point on the path, the height of the lamp post is:

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

\sqrt{2} α

\frac{1}{\sqrt{2}} \tan α

\sqrt{2} r tan α

\frac{r}{\sqrt{2}} \cot α

answer is C.

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

Suppose,
Lamppost height AM= h
Circular path radius OA=OB=r
At any point on the circle, AB subtends an angle of 45 degrees. As a result, it will subtend a 90-degree angle in the middle.
Question Image

OAB is a right-angled triangle, right angle at O.
Using the Pythagorean theorem,

{\Rightarrow OA}^{2} + {OB}^{2} = {AB}^{2}

\Rightarrow r^{2} + r^{2}

= {AB}^{2}

\Rightarrow {AB}^{2} = 2 r^{2}

AB = r \sqrt{2}

△ AMB we have,

\tan α = \frac{AM}{AB}

\Rightarrow \tan α = \frac{h}{r \sqrt{2}}

\Rightarrow h = r \sqrt{2} \tan α

Thus, height of the lamppost =

r \sqrt{2} \tan α

Correct option is 3.

Watch 3-min video & get full concept clarity

courses

No courses found

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Online Course for IIT JEE

Best Online Course for NEET

Best Online Course for CBSE

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Get Expert Academic Guidance – Connect with a Counselor Today!