Question

Suppose a triangle has sides a, b, and c. Let theta be the angle opposite the side of length b. If cos theta > 0, what must be true?

A. a^2 + b^2 = c^2
B. a^2 + c^2 > b^2
C. a^2 + c^2 < b^2
D. a^2 + b^2 > c^2