### Scribe Post for May 25, 2010

Tuesday, May 25, 2010

Today in math class, we learned about tangents of a circle. First of all, what is a tangent (of a circle)?
A tangent is:
-a line that touches a circle at exactly one point
-the point where the line touches the circle is called the point of tangency

We also learned how to use the tangent chord relationship to find the unknown lengths, given in the diagrams. We used the Pythagorean theorem (only if there's a right triangle).
for example:
-find the length of AB (if BC (diameter) is 14 cm, and AC (hypotenuse) is 20 cm)
solution:

Then we learned how to determine angle measures in a circle with a tangent line.
-find the measure of angles A,B,C

To find A
180°=A+42°+90°
180°-132°=A
48°=A

To find C
Since C, is subtended by the same arc as A, A could be divided by two, then you'll get 24° for C.

To find B. (A+B=diameter(which is always 180°)
A+B=180°
48°+B=180°
B=180°-48°
B=132°

After those two examples, we had another example using the tangent chord relationship, once again.
-find the measure of line DE
solution:

Today's homework are:
-10.3 textbook
-CYU #2
-Practice (odd)
-Apply : ALL
-Extend 19&21
-Workbook, and Extra Practice
-journal
TEST ON FRIDAY

For Tuesday, June 1
hand in inside stash-its
-problems of the week (#3, and another)
-journal
-last test signed