If the line segment joining the points \( (1,0) \) and \( (0,1) \) subtends an angle of \( 45^\circ \) at a variable point \( P \), then the equation of the locus of \( P \) is:
200 g of water is heated from 40°C to 60°C. The change in its internal energy [No expansion is taken place] specific heat of water is 4200 J kg⁻¹ K⁻¹