Home Geometry Problems All Problems Circle 481-490 Solution / comment        By Antonio Gutierrez
Problem 490. Tangent Circles, Arc, Radius, Circular Sector, Area.
Level: High School, College, SAT Prep.

The figure shows the circles of centers A, B, and C tangent at D, E, F. The measure of the arc DE is 130 degrees and the arc DF is 150 degrees. If the radius of circle C is 3, find the area of the circular sector ECF.

Circular sector area

 

Geometry problem solving is one of the most challenging skills for students to learn. When a problem requires auxiliary construction, the difficulty of the problem increases drastically, perhaps because deciding which construction to make is an ill-structured problem. By “construction,” we mean adding geometric figures (points, lines, planes) to a problem figure that wasn’t mentioned as "given."
 

How to Solve It, Interactive Mind Map

George Pólya's 1945 book "How to Solve It, A new aspect of Mathematical Method", is a book describing methods of problem solving. It suggests the following steps when solving a mathematical problem: (1) First, you have to understand the problem. (2) After understanding, then make a plan. (3) Carry out the plan. (4) Look back on your work. How could it be better? 
 

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