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Mathematics 15 Online
OpenStudy (daisy.xoxo619):

Given: HB PERP. AD EC PERP AD AB CONG CD FA CONG FD Prove: ANGLE AHB CONG. ANGLE DEC

OpenStudy (daisy.xoxo619):

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OpenStudy (radar):

is ADF a triangle, do lines AF and DF join at the top?

OpenStudy (daisy.xoxo619):

YES they do . sorry bad diagram

OpenStudy (anonymous):

so in triangle AHB and triangle CED bcoz FA= FD ==> <A = <D (angles opposite to equal sides are equal) <B = <C (each equa; 90 HB PERP. AD EC PERP AD )

OpenStudy (anonymous):

so remaing <H and <E are also equal

OpenStudy (radar):

Since that is the case, angles BAH and CDE are equal as they are opposite equal sides of a triangle. matricked has already explained also.

OpenStudy (anonymous):

Alternatively in triangle AHB and triangle CED <B = <C (each equa; 90 HB PERP. AD EC PERP AD ) <A = <D (as shown earlier) AB = CD so triangle AHB and triangle CED are congruent hence <AHB =< DEC (corresponding parts of congruent triangles)

OpenStudy (daisy.xoxo619):

by what theorem / postulate is <H CONG<E

OpenStudy (anonymous):

<H = 180 - <A - <B [<A = <D and <B = <C ] = 180 -<D-<C =<E

OpenStudy (radar):

The sum of the interior angles equals 180 degrees in a triangle. You have two angles of one triangle equal to the corresponding angles of another triangle, There sum would be equal thus the sum subtracted from 180 degrees would reveal the third angle would also be equal/

OpenStudy (daisy.xoxo619):

thank you so much @matricked and @radar I think I got it :)

OpenStudy (anonymous):

yw

OpenStudy (radar):

You're welcome, equals subtracted from equal, the remainder will also be equal; Good luck with your studies.

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