Page:An introduction to linear drawing.djvu/37

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14, Describe a circle and draw a tangent to it.

Tangent comes from a latin word, which means to touch. A tangent is a right line which touches a cir- cle, but does not cut any of it off. If a right line be drawn from the centre of the circle or arc to the point of contact (that is, the point where the tangent touches the circle) the two right lines, (that is, the radius and the tangent) will be perpendicular to each other, (fig.9.)

The monitor may test this with his quadrant of pasteboard ; or, marking two places on the tangent at equal distances from the point (f contact, he may see with his dividers if these points are at equal distances from the centre of the circle.

15.	Draw four tangents to a circle, forming a quadrilateral or four sided figure.

This figure need not form a perfect square, as in figure 10.

16.	Circumscribe or surround a circle with a square.

(fig- 8.)

(fig. 10.)