derivation of the formulas used in every section

Sketch a isometric drawing for each of the three sets of orthographic drawings

Why is important to use different line conventions?

Which side of a particular scale should I use if I want to draw these lines on a paper . For example I have 1) architect scale with the following dimensions : 1; 1 1/2; 16 ; 3/32; 3/4;1/8.  2. Engineering scale : 10; 20; 30; 60; 40;50 3.  metric scale : 1:100; 1:20; 1:50; 1:75;1:25;1:125