Simplify. cos^2[(pi/2) - x] + cos^2[(pi/2) - x] + cos^2x

Answer is

    tan²(x) + 1



identities:
   
   

   

   

so

   

notation-wise,  and etc.

   

using the first two identities i have introduced above:

   

using pythagorean identity  we have

   

so it simplifies to tan²(x) + 1

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