Question

In a geometry class, the students were asked to prove the theorem below by contradiction:
Theorem: A quadrilateral cannot have three and only three right angles.
Heather begins the proof with an assumption. Which statement will she most likely use as an assumption?

Answer 1

Select one:
a. Let one angle of a quadrilateral be acute and the other three angles obtuse.
b. Let all angles of a quadrilateral measure 90° each.
c. Let all angles of a quadrilateral be acute.
d. Let one angle of a quadrilateral be obtuse and the other three angles measure 90° each.

Answer 2

@Callisto

Answer 3

sum of all internal angles in a quadrilateral myst be 360 degrees, no matter how u draw it

Answer 4

so if sum equals 360, and u have 3 angles that are 90 each, other angle must equal 90

Answer 5

answer is d.
because we are using contradiction the assumption should be proved wrong in the end

Answer 6

I was just about to say that thnx

Answer 7

my pleasure

Answer 8

To be fair, I personally think the opening statement should be let there be a quadrilateral with 3 right angles and the fourth angle not a right angle (either acute or obtuse).

To make it faster.

Oh well, choice D is still better than the other three, I suppose.