we know that
The Law of Syllogism says that if the following two statements are true:
(1) If p -------> then q .
(2) If q-------> then r .
Then we can derive a third true statement:
(3) If p--------> then r .
In this problem
(1) If a triangle is an isosceles triangle, then it has two sides of equal length
(2) If a triangle has two sides of equal length, then it has two angles of equal measure
Let
p-------> the statement " an isosceles triangle"
q--------> the statement " has two sides of equal length"
r---------> Â the statement "has two angles of equal measure"
Then (1) and (2) can be written
1) If p , then q .
2) If q , then r .
So, by the Law of Syllogism, we can deduce
3) If p , then r
or
If a triangle is an isosceles triangle, has two angles of equal measure
therefore
the answer is
The argument is valid by the law of syllogism.
