Question 1176903
i believe the formula should be:


L = sqrt(H^2 + W^2)


L is the length of the brace which is the hypotenuse of the right triangle formed.
H is the vertical height of the right triangle formed.
W is the hoziontal length of the right triangle formed.

you are given that the brace is 9 meters from the corner of the frame.
that corresponds to W.


you are given that the length of the brace is 12 meters long.
that corresponds to L.


from the formula of L = sqrt(H^2 + W^2), you get:


12 = sqrt(H^2 + 9^2)


square both sides of this equation to get:


144 = H^2 + 81


subtract 81 from both sides of this equation to get:


144 - 81 = H^2


combine like terms to get:


H^2 = 63


solve for H to get:


H = sqrt(63) = 7.937253933.


that's how far up the corner post the brace needs to go.


you could nail at that point, but, in real life, the nail will probably not be right at the intersection point.