`V-i` graphs of anichrome wire at three different temeperatures `t_(1)`, `t_(2)` and `t_(3)` are shown. From the graph.

Explanation

Slope of line gives resistance
So, `R_(1)=tantheta=R_(0)(1+alphaT_(1))`
`R_(2)=tan(90-theta)=cotheta=R_(0)(1+alphaT_(2))`
`cottheta-tantheta=R_(0)alpha(T_(2)-T_(1))`
or `(costheta)/(sintheta)-(sintheta)/(costheta)=R_(0)alpha(T_(2)-T_(1))`
`R_(0)alpha(T_(2)-T_(1))=(cos2theta)/((sin2theta)/(2)),orT_(2)t_(1)alphacot2theta`