Let (-5,4) be a point on the terminal side of theta

If point (-5,4) is a point on the terminal side of , then angle is obtuse (point (-5,4) is placed in the second quadrant). Consider right triangle with legs 5 and 4 and angle ( is in the first quadrant) adjacent to the leg with length 5. By the Pythagorean theorem and the length of the . Then:

1. ;

2. ;

3. .

In the second quadrant function has the same sign as in the first quadrant and functions have the opposite sign.

Therefore,

1. ;

2. ;

3. .

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