Question

Dik sin a 4/5 dan sin b 7/25 dengan a sudut lancip dan b sudut tumpul maka nilai cos(a-b)

Answer 1

Sin a = depan / miring
cos a = samping / miring

depan = 4
miring = 5

samping = √5² - 4²
= √25 - 16
= √9
= 3

cos a = 3/5

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samping = √25² - 7²
= √625 - 49
= 24

cos b = 24/25

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Cos(A - B) = cosA cosB + sinA sinB
= (3/5)(24/25) + (4/5)(7/25)
= 72/125 + 28/125
= 100/125