Verify the identity.

tan (x+pi/2) = -cot x

Work the left side

tan (x +pi/2) = sin (x+pi/2) / cos (x+pi/2)

Now you should know that sin(x+pi/2) = cos(x) and cos(x+pi/2) = - sin (x)

if you do not know that you can obtain from the sin (x+y) and cos (x+y) formulaes doing y = pi/2.

Continue:

sin (x+pi/2) / cos (x+pi/2) = cos(x) / [- sin(x)] = - 1 / tan(x) = - cot (x).

Then, we have obtained the right side from the left side, and the identity is verified.

The sentence needs a descriptor of exactly "what" will happen at gurley and marina. in this case, it is the light at the intersection turning green. in this case, the sentence could be rewritten as "the light at the intersection of gurley and montezuma will turn green exactly three seconds after the light at the intersection of gurley and marina."

The answer would be