The cord is attached between two walls. If it is 8 m long, determine the distance x to the point of attachment at B.

The cord is attached between two walls. If it is 8 m long, determine the distance x to the point of attachment at B.

 

 Solution

The diagram is not a right triangle, as it is in 3 dimensions and not on an x,y axis.

Correct approach:
A=0i+1j+4z.
B=?i+0j+2z.

Distance between 2 points in 3d:
sqrt((x2-x1)^2+(y2-y1)^2+(z2-z1)^2).

(x-0)^2 + (0-1)^2 + (2-4)^2.
x^2 + 1 + 4 = 8^2.
x^2=59.
x= sqrt59 = 7.68115.

Now if you check that you will see that it is correct, as opposed to the answer that you all tried to simplify and didn't bother to check your work