1. The problem statement, all variables and given/known data

Given: sec = where 0< <90

and sin(A- )=sinA-3cosA

Determine the solution of

6cosA +3 = 2sinA

for A [-180; 180], rounded off to one decimal digit.

2. Relevant equations

3. The attempt at a solution

3=2sinA - 6cosA

3=2(sinA-3cosA)

=sinA-3cosA

= sin(A- )

Now I can't get rid of the theta