Pertanyaan

Nilai dari cos 10 5 ∘ − cos 1 5 ∘ sin 7 5 ∘ + sin 1 5 ∘ = ...

Nilai dari $\frac{sin 7 5 ^{\circ} + sin 1 5 ^{\circ}}{cos 10 5 ^{\circ} - cos 1 5 ^{\circ}}$ = ...

-1
1

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Habis dalam

Klaim

Y. Laksmi

Master Teacher

Mahasiswa/Alumni Universitas Negeri Semarang

Jawaban terverifikasi

Pembahasan

Ingat! sin A + sin B = 2 sin (A + B) . cos (A - B) sin A -sin B = -2 sin (A + B) . cos (A - B) sin A = cos

Ingat!

sin A + sin B = 2 sin (A + B) . cos (A - B)
sin A - sin B = -2 sin (A + B) . cos (A - B)
sin A = cos

$begin mathsize 12px style fraction numerator sin space 75 degree plus sin space 15 degree over denominator cos space 105 degree minus cos space 15 degree end fraction equals fraction numerator 2 sin begin display style 1 half end style open parentheses 75 degree plus 15 degree close parentheses times cos begin display style 1 half end style open parentheses 75 degree minus 15 degree close parentheses over denominator negative 2 sin 1 half open parentheses 105 degree plus 15 degree close parentheses times sin 1 half open parentheses 105 degree minus 15 degree close parentheses end fraction equals fraction numerator 2 sin 45 times cos 30 over denominator negative 2 sin 60 times sin 45 end fraction equals fraction numerator 2 sin 45 times cos 30 over denominator negative 2 cos 30 times sin 45 end fraction equals negative 1 end style$