315∘=45∘ less than a full circle XXXi.e. 315∘≡−45∘ csc(−45∘)=1sin(−45∘)=−1sin(45∘)=−√2
Explanation:
Since (−45∘) is in Quadrant IV, sin (and therefore csc) is negative.
The 45∘ angle is a no-right angle in a right-angled equilateral triangle. If the equal length arms of the triangle are of length 1, then the hypotenuse is of length √2 (Pythagorean Theorem).