3D trig

**anonymous_maths** · September 22nd 2009, 06:46 PM

Help me with this question please

http://i667.photobucket.com/albums/v...0001/wedge.jpg

Thank you in advance

**Grandad** · September 23rd 2009, 04:45 AM

Hello anonymous_maths

Originally Posted by anonymous_maths

Help me with this question please

http://i667.photobucket.com/albums/v...0001/wedge.jpg

Thank you in advance

I'm assuming that all the angles at $B$ and $C$ are right-angles.

Then, in the diagram I've attached, $N$ is the required point on $FE$ ; $P$ is the foot of the perpendicular from $N$ to the base; and the required angle, $a = \angle NDP$ .

Then, from $\triangle NDP,\, \tan a = \frac{NP}{DP}= \frac{6}{DP}$

$\Rightarrow DP = \frac{6}{\tan a}$

Note now that $FN = CP$ , and then consider $\triangle DPC$ . By Pythagoras' Theorem: $CP^2 = DP^2 - DC^2$

$\Rightarrow FN = CP = \sqrt{\Big(\frac{6}{\tan a}\Big)^2- 12^2}=\sqrt{\frac{36}{\tan^2a}-144}$

Grandad

Thread: 3D trig

LinkBack

Thread Tools

Display

3D trig

Similar Math Help Forum Discussions

Compute Trig Function Values, Solve Trig Equation

A few trig problems- help please (double angle and simplifying trig expressions)

Trig ratios, other trig mapping questions :/ Help greatly appreciated

Another question proving that a trig equation follows from another given trig equatio

Can someone check my Trig (Trig Form and Demoive's Theorm

Search Tags