Trigonometry  Trigonometric Equations.
Summary of strategies.
To solve trigonometric equations, follow these strategies to identify what type of equation you have and what the relevant strategy is:
Equation type  Characteristic of this type of equation.  Strategy 
1.  One trig term and a constant. 

2.  One trig term squared and a constant. 

3.  Two trig terms  one a cos and one a sin  and NO constant. 

4.  A quadratic equation with a squared trig ratio, a usual trig ratio and a constant term. 

5.  Other formats.  Reduce other formats to their basic components with factorisation  then use one of the above strategies as appropriate. 
6.  Double angle (sometimes triple)  for example  2θ or 3θ  applies to all of the above  When the angle is expressed as a multiple:

Examples.
Solve the following equations for 0 ≤ θ ≤ 360°.
Equation type  Characteristic of this type of equation.  Strategy 
1.  2 sin θ  1 = 0 One trig term and a constant. 

2.  4 cos^{2}θ  1 = 0 One trig term squared and a constant. 

3.  sin θ  cos θ = 0 Two trig terms  one a cos and one a sin  and NO constant. 

4:  3sin^{2}θ  sin θ  4 = 0 . A quadratic equation with a squared trig ratio, a usual trig ratio and a constant term. 

5:  sin θ cos θ + sin θ = 0 Other formats. 

6.  sin 2θ = ½ The angle is a multiple of θ.

sin 2θ = ½ (need to go two revolutions) ∴ 2θ = 30°, 150°, 390°, 510°. θ = 15°, 75°, 195°, 255°. 