Answer:
As mentioned ABCD is a square
So <DEC is always 90 degree
Answer:
<h2>This triangle is a right triangle:</h2><h2>36² + 15² = 39².</h2>
Step-by-step explanation:
If a ≤ b <c is the length of the sides of a right triangle, then:

We have

Check the equality:



It's a right triangle.
Answer:
D.the product is negative
for example
2×-1
=-2