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 1 of 5.
Shyam said:
1 decade ago
Why the above two problem we taking "tan", but for this problem we took "cos". Anyone explain ?
Ashish said:
1 decade ago
Can we do it taking tan?
Nikita said:
1 decade ago
Shyam and Asish,
Absolutely we can take tan.
but if we take tan we will get AB.
Then we have to take sin to find length of the ladder, i.e BC.
It 'll take more time..so only we take cos in this problem.
Absolutely we can take tan.
but if we take tan we will get AB.
Then we have to take sin to find length of the ladder, i.e BC.
It 'll take more time..so only we take cos in this problem.
Shine said:
1 decade ago
Nikita great Ans thanks
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.
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