X}_{1}},{{y}_{1}})\] be the REQUIRED point. From \[P\,({{x}_{1}},{{y}_{1}})\], we draw PM and PN perpendicular to OX and OY respectively. GIVEN, \[PM+PN=2\] ......(i) But, \[PM={{y}_{1}},PN={{x}_{1}}\] Hence from (i), \[{{y}_{1}}+{{x}_{1}}=2\] Thus locus of \[({{x}_{1}},{{y}_{1}})\]is \[x+y=2\] which is a straight line.