Given cscx-sinx=a
=>1/sinx-sinx=a
=>(1-sin^2x)/sinx=a
=>cos^2x/sinx=a
Again secx-cosx=b
=>1/cosx-cosx=b
=>(1-cos^2x)/cosx=b
=>sin^2x/cosx=b
Now a^2b^2(a^2+b^2+3)
=cos^4x/sin^2x xxsin^4x/cos^2x(cos^4x/sin^2x+sin^4x/cos^2x+3)
=sin^2x xxcos^2x((cos^6x+sin^6x)/(sin^2xcos^2x)+3)
=cos^6x+sin^6x+3sin^2xcos^2x
=(sin^2x)^3+(cos^2x)^3+3sin^2xcos^2x(sin^2x+cos^2x)
=(sin^2x+cos^2x)^3=1^3=1
Proved