Help me with this question please
http://i667.photobucket.com/albums/v...0001/wedge.jpg
Thank you in advance
Help me with this question please
http://i667.photobucket.com/albums/v...0001/wedge.jpg
Thank you in advance
Hello anonymous_mathsI'm assuming that all the angles at $\displaystyle B$ and $\displaystyle C$ are right-angles.
Then, in the diagram I've attached, $\displaystyle N$ is the required point on $\displaystyle FE$; $\displaystyle P$ is the foot of the perpendicular from $\displaystyle N$ to the base; and the required angle, $\displaystyle a = \angle NDP$.
Then, from $\displaystyle \triangle NDP,\, \tan a = \frac{NP}{DP}= \frac{6}{DP}$
$\displaystyle \Rightarrow DP = \frac{6}{\tan a}$
Note now that $\displaystyle FN = CP$, and then consider $\displaystyle \triangle DPC$. By Pythagoras' Theorem: $\displaystyle CP^2 = DP^2 - DC^2$
$\displaystyle \Rightarrow FN = CP = \sqrt{\Big(\frac{6}{\tan a}\Big)^2- 12^2}=\sqrt{\frac{36}{\tan^2a}-144}$
Grandad