Help!!

Write the formula for the area of a right triangle if two legs are known.
If the first leg of the triangle is x and the length of the second leg is y, the formula for the area of a right triangle is A = ?

Draw the line of reflection that reflects △abc onto triangle δ a'b'c'

(a) (8%) compute the probability of an even integer among the 100 integers 1! , 2! , 3! , until 100! (here n! is n factorial or n*(n-1)*(n-2) *… 1) (b) (16%) compute the probability of an even integer among the 100 integers: 1, 1+2, 1+2+3, 1+2+3+4, …., 1+2+3+… + 99, and 1+2+3+… + 100

What properties allow transformation to be used as a problem solving tool