To find the cosine of the negative angle, you can use the following trigonometric identity:

cos$-\theta$ = cos$\theta$

Therefore, cos$-SinA$ = cos$SinA$

Since SinA = √3/2, we can use the Pythagorean theorem to calculate the cosine. CosA = ±√$1-Si{n}^2(A)$. So, in this case:

cos$A$ = ±√$1-(\surd 3/2{)}^2$ cos$A$ = ±√$1-3/4$ cos$A$ = ±√$1/4$ cos$A$ = ±1/2

Therefore, the cosine of -SinA is the same as the cosine of SinA, which is ±1/2.