1. ## Vector help

Hi all,

Struggling with three vector questions and would appreciate if someone could help me.

The roof is symmetrical

Determine the vectors AB, BC and CA and in each case calculate the modulus.
Find the direction cosines of AB and hence calculate the angle (correct to 1 decimal place) between AB and each of the positive coordinate axes

Find all the angles (in degrees) in the triangle MDF, correct to 2 decimal places.

Obtain the outward unit normal vector to the sloping roof FGHC

Would really appreciate it

2. Originally Posted by mathsnub

Obtain the outward unit normal vector to the sloping roof FGHC
The cross product of HG and GF will allow you to obtain a normal vector to the region.

3. Originally Posted by mathsnub

Find all the angles (in degrees) in the triangle MDF, correct to 2 decimal places.
M(0,7,3.5), D(6,12,0) and F(3,0,8.5)

Graph these points in 3D and solve for the angles.

To determine all the vectors, make point O the origin like I did hear and determine the vectors and modulus will come easily.