Sana: 201 y. Mavzu: ko'pburchaklar darsning maqsadi

Agar parallelogrammning diagonallari teng bo'lsa, u to'g'ri to'rtburchakdir.
Ushbu teoremani mustaqil isbot qilish o'zingizga havola qilinadi.
Masala. Ikkita qo'shni tomoni a va b bo'lgan to'g'ri to'rtburchakni yasang.
Yasash. A to'g'ri burchak yasaymiz (32-rasm). Uning tomonlarida AD = a va AB = b kesmalarni qo'yamiz. B va D nuqtalar orqali p  AB va q  AD to'g'ri chiziqlarni o'tkazamiz. p  AB va AD  AB bo'lgani uchun p|| AD bo'ladi. q to'g'ri chiziq AD to'g'ri chiziq bilan kesishgani sababli, u unga parallel bo'lgan p to'g'ri chiziqni biror C nuqtada kesadi. Hosil bo'lgan ABCD to'rtburchak — to'g'ri to'rtburchak bo'ladi. Unda yasashga ko'ra A, B va D burchaklar to'g'ri, C burchak ham to'g'ri (Agar to'g'ri chiziq ikkita parallel to'g'ri chiziqdan biriga perpendikular bo'lsa, u ikkinchi to'g'ri chiziqqa ham perpendikular bo'ladi.)
To'g'ri to'rtburchaklarni yasashning boshqa usullari ham bor.
4. Yangi mavzuni yoritish va Yangi mavzuni mustahkamlash:
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