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Math·Geometry and Trigonometry·Right triangles and trigonometry

hard

Triangle $ABC$ is similar to triangle $DEF$, where angle $A$ corresponds to angle $D$ and angle $C$ and $F$ are right angles. The length of $\overline{AB}$ is $2.4$ times the length of $\overline{DE}$. If $\tan A=\frac{21}{20}$, what is the value of $\sin D$?

1

21/29

2

.724

3

0.724

4

.7241