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Mathematics 8 Online
OpenStudy (anonymous):

What is the area of the shaded region in the given circle in terms of pi and in simplest form?

OpenStudy (anonymous):

OpenStudy (anonymous):

@TheSmartOne @amistre64

OpenStudy (campbell_st):

the unshaded area can be found using unshaded area = Area of the sector - area of the triangle so the shaded area = area of the circle - unshaded area

OpenStudy (campbell_st):

you need the trig form of area of a triangle \[A = \frac{1}{2} \times a \times b \times \sin(C)\] the sector area is \[A = \frac{60}{360} \times \pi \times r^2\] hope it helps

OpenStudy (amistre64):

area of the partial circle, plus area of the triangle ... would be my approach

OpenStudy (amistre64):

the hardest thing might be in recalling how to find the area of the triagnle with the information given

OpenStudy (anonymous):

i had left for a min.. but what would i Do, i know he gave me the formula but take me through it @amistre64

OpenStudy (amistre64):

different appraoches but we have part of a circles area, what proportion of the circle do we have? |dw:1431895127949:dw|

OpenStudy (campbell_st):

the triangle has sides of 12 m and an angle 60 degrees so \[Area = \frac{1}{2} \times 12 \times 12 \times \sin(60)\] the sector is \[Area = \frac{60}{360} \times \pi \times 12^2\] then the unshaded are = area of sector - area of triangle

OpenStudy (campbell_st):

last part is Shaded = area of circle (radius 12) - unshaded area

OpenStudy (anonymous):

amistre a full circle is 360 and they give us 60 so the other apart is 300 degrees? and campbell would I leave pi to the side??

OpenStudy (amistre64):

yes 300 out of 360 is the proportion of the full circles area that is shaded 300/360 30/36 15/18 is a simplified ratio. whats the area of a full circle of radius 12?

OpenStudy (amistre64):

3.5/3.6 5/6 is even simpler :)

OpenStudy (amistre64):

\[\frac56(\text{area of full circle})+(\text{area of triangle})=Area_{shade}\]

OpenStudy (amistre64):

\[Area_{\triangle}=2\sqrt{3}\int_{0}^{6}x~dx\]

OpenStudy (anonymous):

these are my options. What would i choose

OpenStudy (amistre64):

im not choosing one for you, we can work the process and come to the solution. your full participation is required.

OpenStudy (anonymous):

lol ok i respect that, 452.39 as the area if the radius was 12

OpenStudy (amistre64):

lets keep it in pi 12^2 pi, our ratio is 5/6 12*12*5/6 pi is the area of interest to us 12*2*5 pi is what?

OpenStudy (anonymous):

12*2=24*5=120

OpenStudy (amistre64):

good, so we want 120 pi to start with now the triangle we have a simple logical way, or the fomula way

OpenStudy (amistre64):

logical way: 45 is less than 60, so its area is less |dw:1431896609447:dw| whats the area of this triangle?

OpenStudy (amistre64):

if we use trapzoid area rule \[A = \frac{base_1+base_2}{2}h\] \[A = \frac{12+0}{2}*6\]

OpenStudy (anonymous):

A=36

OpenStudy (amistre64):

so teh area of a 60 degree angle triangle, is bigger than 36 what does this tell us?

OpenStudy (amistre64):

|dw:1431896914279:dw|

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