1. Construction on the Polar Line started from January 1943. 2. Also, the polar line of a focus of the conic is its corresponding directrix. 3. Let line be the polar line of point with respect to the non-degenerate conic. 4. The concepts of " a pole and its polar line " were advanced in projective geometry. 5. He also made discoveries about projective harmonic conjugates; relating these to the poles and polar lines associated with conic sections. 6. This definition implies that the hyperbola is both the envelope of the polar lines of the points on " B ". 7. Just as uniquely determines its polar line ( with respect to a given conic ), so each line determines a unique pole. 8. For such a conic section, the polar line to a given pole point ( ?, ? ) is defined by the equation 9. Work progressed with limited supplies and those needed for the Polar Line were cannibalized to give way for the airport's completion. 10. The length of polar lines are half that of the equator, and lines of longitude are semiellipses, or portions of ellipses. 
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