Pay attention in class and you would know
It's either a (the first one) or b (the second one), but if I had to choose I would choose b. If I'm wrong I'm so sorry I spent 10 minutes looking at this.
Step-by-step explanation:
Pythagoras Theorem
If the sum of the squares of the smaller two sides is equal to the square if the third side then it is a right triangle

So, (5)^2 + (12)^2
is 25 + 144 = 169
Which is equal to (13)^2 which is also 169
The sides of the given triangle follows pythagoras theorem, therefore it is a right triangle
Hope it helps:)
(-2,2), (4,-4). There are two common ways to attack this problem. The distance formula and Pythagorean theorem. I would use Pythagorean. make line segment cd the hypotenuse of a right triangle. legs would be 6 units and 6 units. a^2+b^2=c^2. 6^2+6^2=c^2. c^2=36+36. c^2=72. c=sq root of 72. c=8.5