Giải thích các bước giải:

a.Gọi $5$ đường thẳng giao nhau tại $O$ là $AA', BB', CC', DD', EE'$
$\to$Các góc có trong hình là:
$\widehat{AOB},\widehat{AOC},\widehat{AOD},\widehat{AOE},\widehat{AOA'}, \widehat{AOB'},\widehat{AOC'},\widehat{AOD'},\widehat{AOE'}$
$\widehat{BOC},\widehat{BOD},\widehat{BOE},\widehat{BOA'},\widehat{BOB'},\widehat{BOC'},\widehat{BOD'},\widehat{BOE'}$
$\widehat{COD},\widehat{COE},\widehat{COA'},\widehat{COB'},\widehat{COC'},\widehat{COD'},\widehat{COE'}$
$\widehat{DOE},\widehat{DOA'},\widehat{DOB'},\widehat{DOC'},\widehat{DOD'},\widehat{DOE'}$
$\widehat{EOA'},\widehat{EOB'},\widehat{EOC'},\widehat{EOD'},\widehat{EOE'}$
$\widehat{A'OB'},\widehat{A'OC'},\widehat{A'OD'},\widehat{A'OE'}$
$\widehat{B'OC'},\widehat{B'OD'},\widehat{B'OE'}$
$\widehat{C'OD'},\widehat{C'OE'}$
$\widehat{D'OE'}$
b.Các cặp góc đối đỉnh là:

$(\widehat{AOB},\widehat{A'OB'}), (\widehat{AOC},\widehat{A'OC'}), (\widehat{AOD}, \widehat{A'OD'}), (\widehat{AOE}, \widehat{A'OE'})$

$(\widehat{BOC}, \widehat{B'OC'}), (\widehat{BOD}, \widehat{B'OD'}), (\widehat{BOE}, \widehat{B'OE'}), (\widehat{BOA'}, \widehat{B'OA})$

$(\widehat{COD}, \widehat{C'OD'}), (\widehat{COE},\widehat{C'OE'}), (\widehat{COA'}, \widehat{C'OA}), (\widehat{COB'}, \widehat{C'OB})$

$(\widehat{DOE}, \widehat{D'OE'}), (\widehat{DOA'}, \widehat{D'OA}), (\widehat{DOB'}, \widehat{D'OB}), (\widehat{DOC'}, \widehat{D'OC})$

$(\widehat{EOA'}, \widehat{E'OA}), (\widehat{EOB'}, \widehat{E'OB}), (\widehat{EOC'}, \widehat{E'OC}), (\widehat{EOD'}, \widehat{E'OD})$