Geometry help! (from Cambridge textbook) (1 Viewer)

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http://community.boredofstudies.org/attachment.php?attachmentid=28127&d=1368959745
Need help with (b) and (c)

 

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View attachment 28127
http://community.boredofstudies.org/attachment.php?attachmentid=28127&d=1368959745
Need help with (b) and (c)

(b)
AD^2 + AG^2 = DG^2 = BG^2
AD^2 + AG^2 = BG^2 (corresponding sides of congruent rectangles)
AD^2 + AG^2 = (AB-AG)^2 (Since BG=AB-AG)
AD^2 + AG^2 = AB^2 + AG^2 - 2AB.AG
AD^2 = AB^2 - 2AB.AG
Rearrange to get the result, sub in to get the answer.

part (c) is easy after doing (b) - just a rectangle minus 2 triangles

 

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Thanks so much!