420 degrees is coterminal with 60 degrees. They point in the same direction. Note how 60+360 = 420. Adding a full revolution onto 60 degrees has us land on 420
So cos(420) = cos(60) = 1/2 using either a calculator, table, or the unit circle.
Similarly,
sin(450) = sin(90) = 1
the angles 90 degrees and 450 degrees point directly north in the same direction. This is why they are coterminal angles. Mathematically, 90 + 360 = 450
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In short,
cos(420) = 1/2
sin(450) = 1
