To find: Value of cosec (-750°)

We have,

cosec (-750°) = - cosec(750°)

[∵ cosec(-θ) = -cosec θ]

= - cosec [90° × 8 + 30°]

Clearly, 405° is in I^st Quadrant and the multiple of 90° is even

= - cosec 30°

= -2 [∵ cosec 30° = 2]