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## High school geometry

### Course: High school geometry>Unit 8

Lesson 13: Constructing a line tangent to a circle

# Geometric constructions: circle tangent (example 2)

Sal constructs a line tangent to a circle using compass and straightedge.

## Want to join the conversation?

• How does the fact of line PC being a diameter of the circle make the triangle a right angle?
• at Sal said that "all the points on this circle are equidistant from c" and then later for point p as well but that doesn't seem to be correct because not all the points in a circle are equidistant from the centre only all the points on the CIRCUMFERENCE are. right?
• Listen again carefully to the video at .
Sal says that all the points on the BLUE circle are equidistant from C and that all the points on the YELLOW circle are equidistant from P.
It's only the 2 points of intersection of the blue and yellow circles that are equidistant from both C and P (because the 2 circles have the same radius).
• Where is that "other video"?
• Are there the exercises for this ?
• how do i calculate the circle equation, if i only have the radius of the circle, and the tangent line to the circle - (the value of it)?
• So can I prove the supplementary angle rule in tangents through this constructions... Have a presentation tomorrow ....
• Can you also do that by making a circle with a radius equals to CP, then we center it at C and choose another point on the circle so C is equidistant from P and the other point meaning it sits on the perpendicular bisector and we draw the radius ??
• At , didn't Sal say to go through point "P"?
Why did he add a point AT "P"?