Does Anyone know slope?

NEED ASAP

Ahypothesis is: a the average squared deviations about the mean of a distribution of values b) an empirically testable statement that is an unproven supposition developed in order to explain phenomena a statement that asserts the status quo; that is, any change from what has been c) thought to be true is due to random sampling order da statement that is the opposite of the null hypothesis e) the error made by rejecting the null hypothesis when it is true

If tan2a=cot(a+60), find the value of a, where 2a is an acute angle

The measurement of one angle of a right triangle is 42° what is the measurement of the third angle? (there is no picture)