Aim: How do we calculate the area of rectangles and triangles?

Aim: How do we calculate the area of rectangles and triangles?
Answer:
                                                       RECTANGLES
Rectangle Area Conjecture:
                      The area of a rectangle, is given by the formula B*H=A, where b is the length of the base, H is the height of the rectangle, and A is the area of the rectangle.
Example:
                                                                                    
http://www.k6-geometric-shapes.com/image-files/formula-area-rectangle.jpg

http://www.algebra-class.com/images/area-rectangle.gif

When a base or height is missing from the equation the formula or a way to find the missinng number is shown below:
TO FIND MISSING BASE: B*H/H=A/H ==>B=?(answer or missing base)
                                                   OR
TO FIND THE MISSING HEIGHT: B/B*H=A/B ==>H=?(answer or missing base)
Example:
B*4/4=24/4==> B=6(answer)
5/5*H= 35/5==>H=7(answer)

                                                              TRIANGLES 
Triangle Area Conjecture:
                   The area of a triangle is given by the formula A=1/2 bh, where A is the area, b is the length of the base, and h is the height of the triangle. The area of the triangle can be seen as ha;f a rectangle which is seen in the second figure.
Example:
http://www.calculateme.com/cArea/area-triangle-base-height.gif

http://etc.usf.edu/clipart/50200/50211/50211_area_triang_lg.gif

If the base or height is missing from the equation a way to find the missing number is shown below:
A=1/2bh ==> A/b=1/2(b/b)(?) ==>A=1/2*2(?) ==> 2(A(after area is divided by base ))=?(answer or missing base)
                                                                OR
 A=1/2bh==>A/h=1/2*(?)(h/h)==> A=1/2*2(?)==> 2(A(after area is divided by height))=(answer or missing height)

Example:
48/12=1/2(12/12)(h)                                                           48/8=1/2(b)(8/8)
4*2=1/2*2(h)                                         OR                        6*2= 1/2*2(b)   
8=h                                                                                      12=b


TRY IT YOURSELF!!!!

What is the area of the following figure?

http://img.sparknotes.com/figures/2/2e8a313ab87d8d9656417d9ad2b59f65/problem_rectangle1.gif




What is the area of the triangle?





http://04.edu-cdn.com/files/static/learningexpressllc/9781576857458/AREA_OF_POLYGONS_28.GIF

Answer:
b*h/2==> 7*6/2==> 42/2==> Answer: 21cm^2