Solving trig. functions (1 Viewer)

[BlueGas]

How do I do what it says in the yellow box? How do I get 90 degrees, 270 degrees, etc.

 

[calamebe]

Well for this question, cos((pi/4)t)=0. When cos(x) is 0, x is pi/2, 3pi/2, 5pi/2 etc. So when solving cos((pi/4)t)=0, we need (pi/4)t to be equal to pi/2, 3pi/2, 5pi/2, and 7pi/2, as I'm guessing the domain was restricted. So then we solve for t to get t=2, 6, and 10.

 

[keepLooking]

Many (including me) were taught by the phrase "All Stations To Central" or ASTC.

 

[BlueGas]

Many (including me) were taught by the phrase "All Stations To Central" or ASTC.

I know how to get 90, and 270 by using ASTC, but I don't know how to get further than that.

 

[calamebe]

I know how to get 90, and 270 by using ASTC, but I don't know how to get further than that.

So is it that you don't know how to get angles greater than 360? If so, what you do is instead of starting at 0 degrees, as you normally do, you can start at 360 degrees. Or you could get the basic angles you need, in this case 90 and 270, and then add 360 degrees to them, to get 450 and 630. If the domain is greater, for instance 0<x<1080, then you would also add 720 to the angles.

 

[keepLooking]

I know how to get 90, and 270 by using ASTC, but I don't know how to get further than that.

It is two revolutions, basically when you know cos theta = 0, theta can be 90, 270, 450 ....,
so you just add 360 for a full revolution to start at the first quadrant again.

 

[BlueGas]

It is two revolutions, basically when you know cos theta = 0, theta can be 90, 270, 450 ....,
so you just add 360 for a full revolution to start at the first quadrant again.

So is it that you don't know how to get angles greater than 360? If so, what you do is instead of starting at 0 degrees, as you normally do, you can start at 360 degrees. Or you could get the basic angles you need, in this case 90 and 270, and then add 360 degrees to them, to get 450 and 630. If the domain is greater, for instance 0<x<1080, then you would also add 720 to the angles.

How about if sinx = 1/2? x = 30, x = 150, and what do I do now?

 

[calamebe]

How about if sinx = 1/2? x = 30, x = 150, and what do I do now?

Are you looking for angles greater than 360? Well add 360 to them, to get x = 390 and x = 510. Also have you learnt general solutions. I don't know whether they are 2 unit or 3 unit but they are useful in calculating angles greater than 360 and less than 0.

 

[keepLooking]

How about if sinx = 1/2? x = 30, x = 150, and what do I do now?