
The distance travelled by the person d will be equal to the arch length.
⇒d=Rθ
⇒60=R(43π)
⇒R=3π60×4=π80m
Now the magnitude of displacement can be found using subtraction of vectors. Therefore,
∣s∣=R22+R12−2R1R2cosθ⇒∣s∣=R2+R2−2R2cos135∘
⇒2R2−2R2(−0.7)
⇒3.4R2=3.4(π80)2
⇒R=47m