Answer:
Here, to find the value of cosec at -1485° angle we need to make sure that we know the CAST FORMULA. We might need to use formula of cosec at 90-x or 90+x or 180+x or 360-x and so on.
But how do we know which one is the correct? So, let me give you a quick trick!
We have,
(-1485°)
Let's try to reduce it somewhere around (0°) by adding (360°)
Here we start,
(-1485° + 360°) = (-1125°)
Again,
(-1125° + 360°) = (-765°)
Again,
(-765° + 360°) = (-405°)
Again,
(-405° + 360°) = (-45°)
We got the value less than 360°
Now we know that
Cosec (-x) = - Cosec x
So,
Cosec (-1485°) = Cosec(-45°) = -Cosec 45° = -√2
So, there we go. A detail explanation on finding the values of Cosec(-1485°).
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