Let A=[−1,1],B=[−1,1],C=[0,∞). Define R1={(x,y)∈A×B:x2+y2=1} and R2={(x,y)∈A×C:x2+y2=1}. Then choose the correct option:
A
R1 is a function and range is [0,1]
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B
R2 is a function and range is [0,1]
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C
R1 is a function and range is [−1,1]
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D
R2 is a function and range is [−1,1]
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Solution
The correct option is BR2 is a function and range is [0,1] Consider R1 For x=0, y can have two values, either 1 or −1. This violates the definition of a function. Hence, R1 is not a function.
Consider R2 x2+y2=1 ⇒y=√1−x2[∵y∈C] For each x∈[−1,1], only one value of y is possible. Hence, R2 is a function.
Now, for the range of R2 −1≤x≤1 ⇒0≤x2≤1 ⇒0≤1−x2≤1 ⇒0≤√1−x2≤1 ∴y∈[0,1] So, the range of R2 is [0,1]