Tolong dibantu yah para master mm,makasih nomor 16 dan 17

16) (cos a)/a + (cos b)/b + (cos c)/c
= [(b^2 + c^2 - a^2)/(2bc)]/a + [(a^2 + c^2 - b^2)/(2ac)]/b + [(a^2 + b^2 - c^2)/(2ab)]/c
= (b^2 + c^2 - a^2)/(2abc) + (a^2 + c^2 - b^2)/(2abc) + (a^2 + b^2 - c^2)/(2abc)
= (a^2 + b^2 + c^2)/(2abc)

17) jarak (P, AB) = 3 jarak (P, CD)
=> AX = 3 DX
=> AX/DX = 3/1
=> AX : DX = 3 : 1
Anggap panjang AX = 3y dan panjang DX = y
Misal panjang AB = DC = k cm
Luas CDXY = a
=> CD . DX = a
=> k . y = a
=> a = ky
Luas ∆ ABP = b
=> 1/2 . AB . AX = b
=> 1/2 . k . 3y = b
=> b = 3/2 ky

Jadi a : b = ky : 3/2 ky = 1 : 3/2 = 2 : 3