# math

posted by
**Anonymous**
.

Let I denote the interval [0,oo). For each r ∈ I, define

A={(x,y)∈ RxR:x^2+y^2=r^2}

B={(x,y)∈ RxR:x^2+y^2<=r^2}

C={(x,y)∈ RxR:x^2+y^2<r^2}

Determine

UA and ∩A

UB and ∩B

UC and ∩C

posted by
**Anonymous**
.

Let I denote the interval [0,oo). For each r ∈ I, define

A={(x,y)∈ RxR:x^2+y^2=r^2}

B={(x,y)∈ RxR:x^2+y^2<=r^2}

C={(x,y)∈ RxR:x^2+y^2<r^2}

Determine

UA and ∩A

UB and ∩B

UC and ∩C