Monday, February 8, 2010

What Does it take for a compound conditional statement to be false? Any examples?

I don't really get this, I was told that a compound conditional statement could be false. ';If a figure is a parallelogram and has four right angles, then it is a rectangle'; How can that be false? Any other examples would be apreciated. I wana understand this not just write down the answer. Thanks.What Does it take for a compound conditional statement to be false? Any examples?
A condition is only false when the hypothesis is true, and the conclusion is false. So in the example you gave, that is never false, because then you would have to find a parallelogram with 4 right angles that wasn't a rectangle.





If the ground is wet, then it is raining. This would be false when the ground is wet, and it isn't raining (like if the sprinkler went off)What Does it take for a compound conditional statement to be false? Any examples?
You seem to be confusing ';truth value'; with ';self consistent.'; When we look at your statement in English, it seems to be always true by the very definitions of figure, parallelogram, right angle, and rectangle. But as a statement in logic, it can be true or false based on what ';a figure'; is.





Stated somewhat more traditionally it would be: ';If x is a figure, x is a parallelogram and x has 4 right angles, then x is a rectangle.'; This statement by itself is neither true or false: it is an open statement. X can take on many values: the rectangle over there, the triangle on my face, the apple in the fruit bowl. When x is (what a standard #10 envelope looks like), each of the three substatements in the antecedent is true, therefore the conclusion is true. When x is (what the Earth looks like from space), then x is a figure, but x is not a parallelogram, nor does x have 4 right angles: therefore the conclusion is false.





Hope this helps a bit.
consider the square. 4 90 degree angles but with 4 equal sides it is not a rectangle.

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