Question

Sekali lagi
[tex] \: \: [/tex]
Jika:

sin A = 3/5

Maka:
cos 2A = ...
​

Answer 1

Jawaban:

cos 2A = 1-2sin^2 A

cos 2A = 1- 2(3/5)^2

cos 2A = 1-2(9/25)

cos 2A = 7/25

Answer 2

Jawab:
⁷/₂₅

Penjelasan dengan langkah-langkah:
sin (A) = d/m
sin (A) = ³/₅
→ d = 3,
→ m = 5
Cari s
s = √(m²-d²)
s = √(5²-3²)
s = √(25-9)
s = √16
→ s = 4

cos(2A)
= 2cos²(A) - 1
= 2cos²(cos⁻¹(s/m)) - 1
= 2cos²(cos⁻¹(⁴/₅)) - 1
cos²(cos⁻¹(x)) = x², maka
= 2(⁴/₅)² - 1
= 2(¹⁶/₂₅) - 1
= (³²/₂₅) - 1
= (³²/₂₅) - (²⁵/₂₅)
= ⁷/₂₅

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