Aptitude - Height and Distance - Discussion
Discussion Forum : Height and Distance - General Questions (Q.No. 3)
3.
The angle of elevation of a ladder leaning against a wall is 60° and the foot of the ladder is 4.6 m away from the wall. The length of the ladder is:
Answer: Option
Explanation:
Let AB be the wall and BC be the ladder.
Then, 
ACB = 60° and AC = 4.6 m.
| AC | = cos 60° = | 1 |
| BC | 2 |
 BC |
= 2 x AC |
| = (2 x 4.6) m | |
| = 9.2 m. |
Discussion:
45 comments Page 4 of 5.
Shiyamala maths said:
1 decade ago
sin=Opposite side/hypotenuse
cos=adjacent side/hypotenuse
tan=opposite/adjacent
AC=4.6
We know adjacent side that is only we are using cos
cos{60)=A.s/Hypo=1/2
=AC/AB = 1/2 {cross multiplication)
=2(AC)=AB
2(4.6)=AB
9.2=AB
cos=adjacent side/hypotenuse
tan=opposite/adjacent
AC=4.6
We know adjacent side that is only we are using cos
cos{60)=A.s/Hypo=1/2
=AC/AB = 1/2 {cross multiplication)
=2(AC)=AB
2(4.6)=AB
9.2=AB
Cynthia said:
1 decade ago
Why can't we take in this way:
Tan 60 = AB/4.6.
1.73 = AB/4.6.
AB = 7.958.
Tan 60 = AB/4.6.
1.73 = AB/4.6.
AB = 7.958.
Anand said:
1 decade ago
Short cut of sin, cos, tan are.
sin = old/harry (opposite/hypotenuse).
cos = and/his (adjacent/hypotenuse).
tan = old/aunty (opposite/adjacent).
(note:check first letter).
sin = old/harry (opposite/hypotenuse).
cos = and/his (adjacent/hypotenuse).
tan = old/aunty (opposite/adjacent).
(note:check first letter).
Vikram said:
1 decade ago
Why we are using cos here?
Fgrg said:
1 decade ago
Can't we do this with the 30, 60, 90 triangle method?
Anant said:
1 decade ago
tan60 = x/4.6.
x = tan60*4.6.
x = 1.732*4.6.
Therefore, x = 7.8.
x = tan60*4.6.
x = 1.732*4.6.
Therefore, x = 7.8.
Neeraj said:
7 years ago
Why can't we solve this using tan?
Manjunath said:
10 years ago
They are asking 4.6 m away from the wall. But here its get attach with the wall. How come?
SREEJA said:
9 years ago
How can we remember here we should use "Tan" and there we should use "Cos"?
Rahul RAMI said:
9 years ago
Its very simple @Sreeja.
If we have perpendicular (AB) and say to find hypotenuse (BC) then we use sin Angle.
If we have perpendicular (AB) and say to find Base (AC) then we use tan Angle.
If we have Base (AC) and say to find Hypotenuse (BC) then we use Cos angle.
Note : AB, AC, BC are taken from the solution of this question,
In above example, we have a base (AC) and say to the fine length of ladder means find hypotenuse (BC).
So we can use Cos Angle in this situation.
If we have perpendicular (AB) and say to find hypotenuse (BC) then we use sin Angle.
If we have perpendicular (AB) and say to find Base (AC) then we use tan Angle.
If we have Base (AC) and say to find Hypotenuse (BC) then we use Cos angle.
Note : AB, AC, BC are taken from the solution of this question,
In above example, we have a base (AC) and say to the fine length of ladder means find hypotenuse (BC).
So we can use Cos Angle in this situation.
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