Step 1: Expand (5cosx−3sinx)2.
(5cosx−3sinx)2=25cos2x−2⋅5cosx⋅3sinx+9sin2x=25cos2x−30cosxsinx+9sin2x
Step 2: Expand (3cosx+5sinx)2.
(3cosx+5sinx)2=9cos2x+2⋅3cosx⋅5sinx+25sin2x=9cos2x+30cosxsinx+25sin2x
Step 3: Add the expansions.
(5cosx−3sinx)2+(3cosx+5sinx)2=(25cos2x−30cosxsinx+9sin2x)+(9cos2x+30cosxsinx+25sin2x)
Step 4: Combine like terms.
=25cos2x+9cos2x+9sin2x+25sin2x−30cosxsinx+30cosxsinx=34cos2x+34sin2x+0=34(cos2x+sin2x)
Step 5: Use the Pythagorean identity.
cos2x+sin2x=1
34(cos2x+sin2x)=34⋅1=34
Final answer: 34