what is the tan of 45 degree

think about it for a moment.

You have a right angled triangle.

one of the accute angles is 45 degrees.  umm the angle sum of a triangle is 180 degrees so

the other angle must be 45 degrees too mustn't it?

so we have an isosceles right angled triangle.

the opposite side is the same length as the adjacent side.

so opp/adj = 1

tan45°= 1

The answer is 1