How do you tell whether the value of tan 90 degrees is positive, negative, zero or undefined?, Socratic
SOLUTION: Given that X is an acute angle and COS X = (2√5)/5, find tan (90-x)Given that X is an acute angle and COS X = (2√5)/5, find tan (90-x)
trigonometry - Proving that $\tan \theta=\cot(90^\circ-\theta)$ when $\theta>90^\circ$ - Mathematics Stack Exchange