SOLUTION: Solve the following equation for x in the interval 0 ≤ x ≤ 2π tan(x) = -0.63

First find the reference angle with your calculator.

Make sure your calculator is in radian mode and not degree mode.
Press the MODE key to be sure.

To find the reference angle, use the inverse tangent key, TAN-1.
You'll probably have to press a 2ND key first.

Also be sure to use the positive 0.63 not the negative -0.63.

You'll get 0.5621867439

But that is NOT the answer.

First realize that the tangent is negative in QII and QIV.

To get the answer in the second quadrant QII, subtract from pi.

You have a key for pi on your calculator.  You also may have
to press a 2ND key to get it.

pi = 3.141592654.

To get the QII answer you subtract

3.141592654 - 0.5621867439 = 2.57940591

To get the answer in the fourth quadrant QIV, subtract from 2pi.

You have a key for pi on your calculator.  You also may have
to press a 2ND key to get it.

pi = 3.141592654.

Multiply that by 2

2pi = 6.283185307

To get the QIV answer you subtract

6.283185307 - 0.5621867439 = 5.720998563

Edwin