Download Surface Area of Cones completed

U7 L3 SA of Cones completed.notebook
March 11, 2015
Measurement Relationships
Day 3: Surface Area of Cones
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U7 L3 SA of Cones completed.notebook
March 11, 2015
is a three dimensional solid with a circular base. The lateral surface
is curved and extends from the base to a point called the vertex.
NOTE:The height is the line that hits the base at a 90o angle
and is not to be confused with the slant height.
Developing a formula for surface area of a cone:
The lateral surface is a circle-sector (i.e. a piece of a circle). This sector is
some frac on (one nth) of a circle with radius s (s being the slant height).
Acircle =
Asector =
The circumference of the sector is one nth of the circumference of the whole
circle with radius s.
Ccircle =
Since the circumference of the sector wraps around the circumference of
the base of the cone (which is a circle with radius r), they must be equal in
length. Therefore, we can write the following:
s
So, the formula for Surface area of a cone is:
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U7 L3 SA of Cones completed.notebook
March 11, 2015
EX. 2. The slant height of a cone is tripled. Does this triple the surface area
of the cone? Explain.
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U7 L3 SA of Cones completed.notebook
March 11, 2015
radius. How do the
two cones differ? How are they the same?
EX. 4. The lateral area of a cone with slant height 14 cm is 132 cm2.
a) Find the radius of the cone, to the nearest cm.
b) Find the height of the cone, to the nearest cm.
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U7 L3 SA of Cones completed.notebook
March 11, 2015
one is 8 cm
and the height of the pylon is 31 cm. If only the p
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U7 L3 SA of Cones completed.notebook
March 11, 2015
Practice: pg. 447-449 #2-7, 8, 10, 13
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