Solve the given equation. (Enter your answers as a comma-separated list. Let k be any integer):
7 cos θ sin θ + 2 cos θ = 0

Question

Solve the given equation. (Enter your answers as a comma-separated list. Let k be any integer): 
7 cos θ sin θ + 2 cos θ = 0

anonymous · Answer

I tried it and got $$\theta=\frac{ \Pi }{ 2 } and \frac{ 3\Pi }{ 2 }$$ ...but its wrong

slaaibak · Answer

First factor out the cos theta:

$$\cos(\theta)(7\sin(\theta) + 2) =0$$

$$\rightarrow \cos \theta =0 $$

or

$$7\sin(\theta) + 2 = 0$$

Jut solve those two.

anonymous · Answer

yeah, that's what I did and since the second one you cant find the sine of -2/7 I can't solve for that one. 
Which leaves only pi/2 and 3pi/2 for the first one.

campbell_st · Answer

you can find sin(x)  = 2/7 

then use the angles in any quadrant to fin the solution 

sin is negative in the 3rd (pi + x) and 4th quadrant (2pi - x) 

this will allow you to find all the solutions.