Answer:
(a) see attached
(b) CD = 29
Step-by-step explanation:
(a)
See the attachment for a diagram.
In the diagram, we have shown point E on the plane so that BE is parallel to AC.
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(b)
Triangle BDE is a right triangle with hypotenuse BD = 25 and leg BE = AC = 15. The length DE is given by the Pythagorean theorem as ...
DE = √(BD^2 -BE^2) = √(625 -225) = 20
Triangle CDE is a right triangle with hypotenuse CD and legs CE = 21 and DE = 20. The length of the hypotenuse is also given by the Pythagorean theorem as ...
CD = √(CE^2 +DE^2) = √(21^2 +20^2) = √841
CD = 29
