## THERMAL SCIENCE

International Scientific Journal

### Thermal Science - Online First

online first only
### Harmonicity and differential equation of involute of a curve in E3

**ABSTRACT**

In this paper, we first give necessary conditions in which we can decide whether a given curve is biharmonic or 1-type harmonic and differential equations characterizing the regular curves. Then we research the Frenet formulas of involute of a unit speed curve by making use of the relations between the involute of a curve and the curve itself. In addition we apply these formulas to define the essential conditions by which one can determine whether the involute of a unit speed curve is biharmonic or 1-type harmonic and then we write differential equations characterizing the involute curve by means of Frenet apparatus of the unit speed curve. Finally we examined the helix as an example to illustrate how the given theorems work.

**KEYWORDS**

PAPER SUBMITTED: 2019-07-30

PAPER REVISED: 2019-09-20

PAPER ACCEPTED: 2019-09-29

PUBLISHED ONLINE: 2019-11-02

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