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Jika A + B = π/3 dan cos A cos B = 7/12, nilai cos (A – B) =

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Jika A + B = π/3 dan cos A cos B = 7/12, nilai cos (A – B) = ….

     A.   ¼

     B.    2/3

      C.    ¾

     D.   1

     E.    5/4

Pembahasan:

Kita cari (sin A sin B) terlebih dahulu:

cos (A + B) = cos A cos B – sin A sin B

cos (π/3) = 7/12 – sin A sin B

sin A sin B = 7/12 – ½ = 1/12


Maka:

cos (A – B) = cos A cos B + sin A sin B

                    = 7/12 + 1/12

cos (A – B) = 8/12 = ¾ 

Jawaban: C

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4 comments for "Jika A + B = π/3 dan cos A cos B = 7/12, nilai cos (A – B) ="

Natasya August 11, 2021 at 9:38 AM Delete Comment
This comment has been removed by the author.
Natasya August 11, 2021 at 9:41 AM Delete Comment
maaf.. bukannya 2/3 ya ?
(8/12=4/6=2/3)
Anonymous August 24, 2021 at 2:34 PM Delete Comment
Bukannya kalau disederhanakan jadi ⅔ ya?
Unknown November 17, 2021 at 9:12 AM Delete Comment
kalau soalnya sin gimana