AMC 12A 2022 Problem 12

Past Contests AMC 12 AMC 12A - 2022
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1

Let M be the midpoint of \overline{A B} in regular tetrahedron A B C D. What is \cos (\angle C M D) ?

Answer Choices
A. \dfrac{1}{4}
B. \dfrac{1}{3}
C. \dfrac{2}{5}
D. \dfrac{1}{2}
E. \dfrac{\sqrt{3}}{2}