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#1 2019-03-24 01:17:10

avaeliza
Member
Registered: 2018-10-18
Posts: 2

Areas of Polygons Review

Hello! I have a lesson review that I need some help figuring out. I'll post 3-7 and then the next set if I still need help. Thanks smile

For #1-7, calculate the area for each of the polygons described below. Round answers to the nearest hundredth and remember to include the unit of measure.

Stuck on #3 right now. Here's what I have so far:
#3. A regular pentagon with a side of 3 centimeters
2 x side angle + central angle = 180
2 x side angle + 72 = 180
2 x 54 + 72 = 180
tan(54) ?????????

I followed my teacher's example of a nonagon here:
Find the measure of one base angle.
    central angle = 360/9 = 40
    2 * side angle + central angle = 180
    2 * side angle + 40 = 180
    2 * side angle = 140
    side angle = 70°

Use a trig ratio to find the height of one triangle.
    tan(70°) = h/(8/2)
    h = 4*tan(70°)
    h = 10.99 in

I can't figure out what the h/8/2 part means.



I haven't tried 4-7 yet because I think I might run into the same issues.

#4. A regular hexagon with a side of 10 cm

#5. A regular heptagon with a side of 7 inches.

#6. A trapezoid where the height is 18 cm, base 1 = 16 cm and b2 = 8 cm.

#7. A trapezoid where the height = 7 mm, base 1 = 26 mm and base 2 = 9 mm.

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#2 2019-03-24 14:32:54

Monox D. I-Fly
Member
From: Indonesia
Registered: 2015-12-02
Posts: 2,000

Re: Areas of Polygons Review

For trapezoids, just use ½(base 1 + base 2) ÷ height.


Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.
May his adventurous soul rest in peace at heaven.

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#3 2019-03-24 16:03:14

Jai Ganesh
Administrator
Registered: 2005-06-28
Posts: 45,968

Re: Areas of Polygons Review


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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