If 3sin tita - cos tita=0,how do I find the value of 3tan tita=1(0° less than or equal to tita less than or equal to 360°) with the use of a graph book?

Answer 1

3sin tita - cos tita=0
3sin Ø = cos Ø , ..... theta , not tita
divide both sides by cos Ø
3 sinØ/cosØ = 1
3 tanØ = 1

tanØ = 1/3

By "the use of a graph book", I will assume that you mean the
table of trig values one could find in most math text books in past years.
Since 1/3 = appr .3333, go to the tangent column, find the value closest
to .3333 and note the angle. You should get 18° as the nearest degree.

From your CAST rule, you also know that the tangent trig ratio is positive in quadrants I and III,
so Ø = 18° or Ø = 198°

Answer 2

Ø or φ = phi
Θ or θ = theta

Answer 3

Ø is fast access on my Mac (Option-shift-O), that's why I use it for an angle.