Answer:
Option D: 2 . cos(90 + x) = -2a
Explanation:
Given that:
sin x = a --------- eq1
As we know that trignometry says:
cos(90 + x) = -sinx-------- eq2
In option two we are given that:
cos(90 + x) = -2a ---------- eq3
So by equating both sides of eq2 and eq3:
-2a = -2sinx
By cancelling -2 from both sides we get:
sinx = a
That is given in eq1
hence proved
i hope it will help you!