Calculating Area of Sector in Shaded Part of Diagram

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The discussion focuses on calculating the area of a shaded sector in a diagram by subtracting the area of a triangle from the area of the sector. The area of the entire circle is determined using the formula πr², while the area of the sector is calculated as a fraction of the circle's area based on the angle in degrees (x/360). To find the angle x, participants suggest using the law of cosines or breaking the triangle into two congruent right triangles and applying trigonometric functions.

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I am trying to work out the area of the shaded part of the diagram. I've figured that If I was to work out the area of the triangle (27cm) and take it away from the sector, I'd have the area of the shaded bit.

I'm guessing that I'd have to use trigonometory to find the area of the sector, I really have no idea how to do this, and would appreciate some help. Thankyou
 
Last edited:
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You're on the right track.

You know the area of the entire circle; it's pi times the radius squared.

You also know what fraction of that area is included in the sector; it's x/360, where x is in degrees.

- Warren
 
Last edited:
Thanks for your help
But how would I work out the size of angle X. Would cos, sin or tan have to be used?
 
You know all three sides -- use the law of cosines to find the angles.

- Warren
 
Less elegantly, you can break the triangle into two congruent right-triangles... then apply trigonometry with a right-triangle.
 
Are you sure that the area of the triangle is 27cm?
 

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