Born to Run

Which one is the radius...

and which one is the diameter?

I remember the radius as the one that starts in the 

middle...

...and then RUNS to the outside.

The diameter crosses the entire diagram.

That's it. Work smart, not hard.

Angle Properties Song

Angle Properties - Interior, exterior, corresponding...

Which is which? See...here for more info. (And another great song.)

Work the numbers, not the pictures

When asked for the measure of angle x...

How many people are tempted to...

  a)...              

                        o

...answer   120   ? (Because "x" looks to be twice as big as 60)

       or          

                b)...

...get out a protractor and measure. (And, of course, find that the answer is not one of the 5 choices given.)

                            o

The answer is 30  . The little box at the bottom left                                                                       o

indicates that the two black lines form a 90   angle. 90 - 60 = 30.

The picture is drawn purposely to mislead you. Work the numbers, not the picture.

Some important things to remember are...

All straight lines are 180 degrees.

All interior angles of a triangle add up to 180 degrees.

All interior angles of squares and rectangles add up to 360 degrees.

Complementary? Supplementary?

My students often can't remember which angles are complementary and which ones are supplementary. I always tell them to think of a really cheap wedding, where the complementary (free) drinks are limited to 90. Complementary angles add up to 90 degrees. "C" for "cheap" and "c" for complementary. A "superb" wedding (supplementary) would offer 180 free drinks. supplementary angles add up to 180 degrees. "S" for "superb" and "s" for supplementary. Failing that, I tell them that "c" comes before "s" in the alphabet and 90 comes before 180.

complementary

supplementaryfrom ClipArt, etc.