JEE Mains · Maths · STD 11 - Trigonometrical equations
A bird is sitting on the top of a vertical pole \(20\, m\) high and its elevation from a point \(O\) on the ground is \(45^o \) . It flies off horizontally straight away from the point \(O\). After one second, the elevation of the bird from \(O\) is reduced to \(30^o \) . Then the speed (in \(m/s\)) of the bird is
- A \(20\sqrt 2 \)
- B \(20\left( {\sqrt 3 - 1} \right)\)
- C \(\;40(\sqrt 2 - 1\))
- D \(\;40\left( {\sqrt 3 - \sqrt 2 } \right)\)
Answer & Solution
Correct Answer
(B) \(20\left( {\sqrt 3 - 1} \right)\)
Step-by-step Solution
Detailed explanation
The height or length of an object or the distance between two distant objects can be determind with the help of trigonometric ratios. In \(\Delta PQQ\), \(\tan 45^o\,=\,\frac {PQ}{OQ}\) \(\Rightarrow \,OQ\,=\,20\,m\) In…
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