How to Use Calculator to Find Tangent in 3rd Quadrant

[mrhtutoring]

Please not that I'm solving for X in the video. Not "?".

[Sgth]

If cosine is 1/2, that easily tells me it's 60 degrees x 4

[surfer_guy]

The calculator does not always give you angles in the first quadrant when working with inverse trig. functions. There are also infinitely many angles which will work for this problem. Try -120 degrees.

[carultch]

This is why you get a calculator with a 4-quadrant angle resolver function, called atan2(x, y) or arctan2(x, y).

That way you don't need to think about the quadrant of the angle, it keeps the information about the sign of both of its inputs, and gives you an angle all the way from -pi to +pi radians.

[muhammademran]

Ref ang = arc tan (y/x)
* x & y without signs

Then as both x, y -ve
Use req angle = 180 + ref ang

[chessandmathguy]

Question doesn't ask for x though. It only asks for the tangent of x. So it's just sqrt(3).

[emihayashi]

Thank you for not covering chalkboard with subtitles!

[awvz_]

Why would you use a calculator for this problem? Isn't the answer of 4π/3 (or 240°) obvious?

[nadamahmoud]

I think we we must divide 1/2 ÷ Sqrt3/2