1. ## Trig Equations

Hello. This is a little urgent so hopefully, I'll be able to get answers quickly. I know this may seem rather basic but I'm having some trouble with these two equations. Well, for one of them, I seemed to be able to get most of the answers but one. Could you please answer these in EXACT form and also in radians?

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First one: (The one I'm struggling with)

2sinx - cosx = 0

All I need for this equation is a starting point or working angle(s) and I should be able to finish off the rest.

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Second one: (Just wanted to ask a little question)

sin3x = 0

For -pi ≤ x ≤ 0

My working angle is obviously 0.

That means x = 0 + (2/3)*k*pi where k is an integer

Now for my answers, I got 0 and -2pi / 3. However, with my calculator, there seems to be another solution which is -pi / 3.

Now, I was wondering, what value of k would allow me to get that missing answer?

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Thankyou. All help is of course, appreciated as usual.

2. Originally Posted by sqleung
2sinx - cosx = 0
A hint:divide by cos(x)

Originally Posted by sqleung
sin3x = 0 For -pi ≤ x ≤ 0
In general you need to remember that if sin(x)=a then sin(pi-x)=a too.