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In triangle ABC, AB = AC and angle A is equal to 36˚ Point D is on AC so that BD bisects
(a) Prove that BC = BD = AD.

(b) Let x = BC and let y = CD. Using similar triangles BCD and ABC, write an equation involving x and y.

(c) Let r = y/x. Write the equation from Part (b) in terms of r and find r

(d) Find cos 36˚ and cos 72˚ using Parts a-c. (Do not use your calculator!)

 

Thanks!

 Oct 8, 2020
 #1
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You can find cos 36 and cos 72 using the double angle formula.

 Oct 9, 2020

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