Panjang OA dan OB adalah sama (jari-jari). Sehingga segitiga OAB membentuk segitiga sama sisi-sisi.

<img align="middle" alt="begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell angle OBA end cell equals cell angle OAB end cell row blank equals cell 40 degree end cell end table end style" class="Wirisformula" data-mathml="«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«mo»§#8736;«/mo»«mi»OBA«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#8736;«/mo»«mi»OAB«/mi»«/mtd»«/mtr»«mtr»«mtd/»«mtd»«mo»=«/mo»«/mtd»«mtd»«mn»40«/mn»«mo»§#176;«/mo»«/mtd»«/mtr»«/mtable»«/mstyle»«/math»" role="math" src="data:image/png;base64,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" style="max-width: none;" />

Jadi, jawaban yang tepat adalah C.

Pada gambar berikut, besar&nbsp;<img align="middle" alt="begin mathsize 14px style angle OAB equals 40 degree end style" class="Wirisformula" data-mathml="«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mo»§#8736;«/mo»«mi»OAB«/mi»«mo»=«/mo»«mn»40«/mn»«mo»§#176;«/mo»«/mrow»«/mstyle»«/math»" height="18" role="math" src="data:image/svg+xml;base64,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" style="max-width: none; vertical-align: -4px;" width="84" />. Besar&nbsp;<img align="middle" alt="size 14px angle size 14px OBA" class="Wirisformula" data-mathml="«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mo mathsize=¨14px¨»§#8736;«/mo»«mi mathsize=¨14px¨»OBA«/mi»«/math»" height="18" role="math" src="data:image/svg+xml;base64,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" style="max-width: none; vertical-align: -4px;" width="45" />&nbsp;adalah ....

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matematika

bahasa indonesia

ipa terpadu

fisika

biologi

bahasa inggris

geografi

sosiologi

sejarah

kimia

ekonomi

Pada gambar berikut, besar . Besar adalah ....

Jawaban: