In a right isosceles triangle, why is the tangent of an acute angle equal to 1?

Tan(angle) = opposite/adjacent

For any acute reference angle, the opposite and adjacent legs are congruent (aka equal). So dividing them would lead to 1

For example, we could have an isosceles right triangle with legs of 3 and 3, So
tan(acute angle) = 3/3 = 1