Matematika

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cos 195°+cos75° tolong di bantu

1 Jawaban

  • Cos 195° = - cos (180+15)
    Cos 15 = -cos (45- 30)
    Cos 15 = - cos45.cos 30 + sin 45. Sin 30
    = -1/2 √2 . 1/3 √3 + 1/2 √2 . 1/2
    = -1/4 √6 + 1/2 √2
    = -1/4(√6+√2)


    Cos 75° = cos (30+45)
    =cos 30.cos 45- sin 30. Sin 45
    = 1/2√3 . 1/2 √2 - 1/2 . 1/2√2
    = 1/4√6 - 1/2 √2
    = 1/4 (√6-√2)


    Cos 195° + cos 75° =
    -1/4(√6+√2)


    Cos 75° = cos (30+45)
    =cos 30.cos 45- sin 30. Sin 45
    = 1/2√3 . 1/2 √2 - 1/2 . 1/2√2
    = 1/4√6 - 1/2 √2
    = 1/4 (√6-√2)


    Cos 195° + cos 75° =
    -1/4(√6+√2)


    Cos 75° = cos (30+45)
    =cos 30.cos 45- sin 30. Sin 45
    = 1/2√3 . 1/2 √2 - 1/2 . 1/2√2
    = 1/4√6 - 1/2 √2
    = 1/4 (√6-√2)


    Cos 195° + cos 75° =
    -1/4(√6+√2) + 1/4 (√6-√2) =
    -1/4

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