Triangle MNP has vertices N(2, 2) and P(0, –2). The triangle is symmetric about the y-axis. What is the approximate measure of the largest angle in the triangle?

By symmetry about the y-axis, the third vertex is M(−2, 2). The two equal sides from P each have length √20, and the side MN has length 4. Using the cosine rule for either angle at M or N, cos θ = (20 + 16 − 20)/(2·√20·4) = 0.447, so θ is about 63.4°. Thus the largest angle is approximately 63.6°, choice C.

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