North Carolina

Heeellllooooooooooooooooooooooooooooo! I really love that there are unlimited precalculus problems. This is incredible.

Socorro, New Mexico

Paraphrasing Pedrotti\'s Optics, it is obvious by Fermat\'s principle and the definition of an ellipse that \"A\" an object placed at one focus of an ellipse will produce an image at the other focus. Also, \"B\", an object placed at one focus of a hyperbola will produce a virtual image
at the other focus. Statement A \"is\" obvious based on definition that ellipse is locus of points such that sum of distances from foci to a point on the ellipse is a constant. Statement \"B\" is not the least bit obvious. You do not use Fermat\'s principle. Instead you use angle of incidence equals angle of reflection ... you produce a real image (by using the \"back\") of the hyperboloid and your result is beautiful. Thank you!!!

iowa, usa

Hello hello

us

😁

jaffna, sri lanka

thank you very much for making that course

Toronto, Ontario, Canada.

niiiicccceeee site

Poland

Thank you for creating this website, it\'s of great help when you try to grasp a new concept!

Louisiana

I just wanted to say hello, and I am looking forward to our students who are all working toward earning their HiSET (High School Equivalency Diploma) participating and learning Algebraic concepts through your online course.
Thank you,
Cathy Peters
Director
Community First High School
communityfirsthighschool.com
cathycommunityfirst@gmail.com

From Canada

Hi Dr. Burns your website is an excellent source of all areas of math. I have found this website extremely helpful. I spent time on it and amazed the way you organized every topics! I also read fun facts of you. That\'s awesome!

england

I was just looking for some bitesize and digestible ways to understand inverse variations and stumbled across this site. It is a favourite of mine now.