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Without using a calculator, find the exact values of

  1. sin⁡(15∘)
  2. cos⁡(5π12)

For (a), note that

15∘=45∘−30∘

Remember that

sin⁡(45)=22,sin⁡(30)=12

and

cos⁡(45)=22,cos⁡(30)=32

For (b), note that

5π12=3π+2π12