Equation Icon  h(1)(t;ξμ) = u(t;ξμ)cos φ(t;ξμ), h(2)(t;ξμ) = v(t;ξμ)cos φ(t;ξμ), (3) μ μ μ (15 ) h (t;ξ ) = u(t;ξ )sinφ (t;ξ ), h(4)(t;ξμ) = v(t;ξμ)sinφ (t;ξμ),