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# Coordinates of a missing vertex

This lesson teaches how to find the missing vertex of a rectangle on a coordinate plane. By understanding that rectangle sides are parallel and vertices form right angles, we can determine that the missing vertex shares its x-coordinate with one vertex and its y-coordinate with another.

## Want to join the conversation?

• Kinda not fair, he gets easy ones while us, we get hard ones
• this is confusing how do you do it with out drawing the thing or do you need to
• I don't understand the question, but I'm gonna assume you mean thinking mentally. A wise teacher once said, "when in doubt, write it out." It's ok not to be able to think of it first inside our heads. Drawing the graph is optional, graph paper is easier to read.
• It's kind of confusing, but after 1,000,000,000,000 tries in the Practice: Area and perimeter on the coordinate plane, I finally get it now.

xd
• My estimate if you did 20 tries an hour, you are roughly 3700 years old. Even if you could do 1 try a minute, you would still be 1900 years old. So I guess this is just using the hyperbole of English.
• Hi! I have a question: What exaclty is a vertex? Thanks, 990011389.
• In a (2-dimensional) polygon, a vertex is the intersection of two adjacent sides. Vertices can be thought of as corners.
Note that in any polygon, the number of sides equals the number of vertices.

Have a blessed, wonderful day!
• Is there a way to do this mentally or in our heads, because then we will have to write it out every time. Also it would be much faster….
• How can I find the location of D if ABCD is a trapezoid A (_3,5) B (_5,1) C (_1,_1)
• You can't.
A trapezoid is a quadrilateral with one pair of parallel sides, so either 𝐴𝐵 is parallel to 𝐶𝐷, or 𝐴𝐷 is parallel to 𝐵𝐶, but we don't know which it is, and even if we knew for example that 𝐴𝐵 is parallel to 𝐶𝐷, we still wouldn't know how long 𝐶𝐷 is.
• Can we use systems of equations to solve this with a parallelogram?