Aptitude - Height and Distance - Discussion

@All.

Here, actually, we want to find the (hypotenus) length of the ladder therefore we use "cos" = B/H (length's ledger).

sin=o/h , cos=a/h, tan=o/a,

Here,
o- Opposite side;
h-Hypotnuse;
a- Adjasent side.

Here, why we have used COS?

Because we have to find the length of the ladder and the length of ladder is the hypotenuse, perpendicular is wall nd base is foot from the ladder so as we know cos equals base upon hypotenuse. So, to get results we will use this as the data given to us fits for cos.

Simply remember the code SOHCAHTOA.

SOH - Sine = Opposite/Hypotenuse.
CAH - Cos = Adjacent/Hypotenuse.
TOA - Tan = Opposite/Adjacent.

why we take cos here? Explain please.

Cos = adj/hyp
Cos60= 4.6m/hyp
0.5= 4.6m/hyp
Hyp= 4.6m/.
Therefore Hyp or length of ladder is 9.2m.

@Anil Kumar.

But they have asked BC not AB. Why are you finding AB?

We all know that tan 60=AB/AC.
then, √(3)=AB/4.6,
then,4.6*√(3)=AB,
AB = 1.732 * 4.6.
AB = 7.967.
AB = 8.

@All.

Take, Sin or Cos or Tan;

Sin = opposite/hypothesis
Cos = adjacent/hypothesis
Tan = opposite/adjacent.

Given are as following;

The angle is 60 degree.

The foot of leader is 4.6 m away from the wall (CA) this means 4.6m is adjacent,
A leader is leaning on the wall (CB) this will be hypothesis while determining (adjacent opposite or hypothesis but in real sense, it's the length of the leader!
Now, we can make out that it's Cos and not tan or sin because adjacent CA is given (4.6m) while hypothesis CB is x or unknown.

So,
Cos60 = CA/CB.
CB(x) = 4.6/cos60.
x = 9.2.

Thank You.

Here, they asked about the length of the ladder, not about the hypotenuse.

So the correct answer is 7.8m.