Which theorem is used to find the hypotenuse of a right triangle in a square root spiral?

Correct answer: Pythagoras theorem

The direct answer is C: Pythagoras theorem. In a right triangle, if the perpendicular sides are a and b and the hypotenuse is c, then . Thus . In a square root spiral, the old length and the newly added unit perpendicular are the two legs; Pythagoras gives the next hypotenuse. Option A, Thales theorem, concerns angles in a semicircle and is not the calculation used here. Option B, midpoint theorem, relates a segment joining midpoints to a triangle side. Option C is correct because it directly finds the hypotenuse of a right triangle. Option D, remainder theorem, belongs to polynomial division, not geometry. Memory cue: right triangle plus hypotenuse means Pythagoras.