A Chord. Or another radius!
A tangent.
A tangent line is always perpendicular to the radius.
The Tangent Line to Circle Theorem states that a line is tangent to a circle if and only if it's perpendicular to the circle's radius.
Perpendicular
The radius-tangent theorem is math involving a circle. The radius-tangent theorem states that a line is tangent to a circle if it is perpendicular to the radius of a circle.
The distance from the center of a circle to any point on the circle is called the radius of the circle. The radius is a line segment that starts at the center of the circle and ends at any point on the circle. It is always a straight line and is always perpendicular to the circumference of the circle. The radius is half the diameter of the circle, which is the distance across the circle through the center. The diameter of a circle is always twice the length of the radius. My recommendation ʜᴛᴛᴘꜱ://ᴡᴡᴡ.ᴅɪɢɪꜱᴛᴏʀᴇ24.ᴄᴏᴍ/ʀᴇᴅɪʀ/372576/ꜱᴀɪᴋɪʀᴀɴ21ᴍ/
A tangent is always perpendicular to the radius of a circle. A radius is a straight line going from the center of the circle to the circumference (edge) of the circle. A tangent is a straight line outside the circle that touched the circle at one (and only one) point. When a tangent touches the outside edge of the circle at the same point where a radius touches the edge of the circle, the angle between the radius and tangent line is 90 degrees meaning they are perpendicular.
The line from the center of a circle to the edge is called a radius. The radius can be used in pi and a lot of other things. If you use the radius the wrong way, your answer will be wrong. Most people call it the " line from the center of a circle to the edge of a circle " but it's called the radius.
The radius of a circle is one half of the circle's diameter, any line going from the center of the circle to the circle itself. A line connecting other points on a circle (or on any curve) is called a chord.
tangent
It is the circle's radius
Radius