Answer
a. $ a/c $
b. $\sqrt {1-b^2/c^2}$
Work Step by Step
a. Express sin A in terms of a and c.
$ sin(A)=a/c $
b. Express sin A in terms of b and c.
$ sin(A)=a/c=\sqrt {c^2-b^2}/c=\sqrt {1-b^2/c^2}$
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