According to the length of each side, this triangle satisfies the Pitagoras Theorem, therefore is a rectangle triangle, look
[tex]2^2=(\sqrt{3}\text{ })^2+1^2[/tex]
Now
[tex]cos(C)=\frac{\sqrt{3}}{2},\text{ }sin(A)=\frac{\sqrt{3}}{2}\text{ }\Rightarrow cos(C)\times sin(A)=(\frac{\sqrt{3}}{2})^2=\frac{3}{4}[/tex]
The answer is 3/4.
