An example worth examining happens when β = π 2 {\displaystyle \beta ={\tfrac {\pi }{2}}} . Knowing that cos ⁡ π 2 = 0 {\displaystyle \cos {\tfrac {\pi }{2}}=0} and sin ⁡ π 2 = 1 {\displaystyle \sin {\tfrac {\pi }{2}}=1} , the above expression becomes equal to: