Aptitude - Height and Distance - Discussion

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

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).

Why we are using cos here?

Can't we do this with the 30, 60, 90 triangle method?

tan60 = x/4.6.

x = tan60*4.6.
x = 1.732*4.6.

Therefore, x = 7.8.

@Cynthia.

No wonder girls are dumb.

We want "BC" (the length of the ladder) not "AC" (height of the wall).

@All.

Sin=perpendicular. Upon hypotenuse and cos, =base upon hypotenuse and tan=perpendicular upon base. And in this question, we need hypotenuse so cos is applied.

How can we remember here we should use "Tan" and there we should use "Cos"?

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.

Also according to the position of angle. We decide which one is opposite side and which one is adjacent. So remember the formula for each Sin, Cos, and Tan and solve the problem easily.