Question

MOHON BANTUANNYA. DENGAN CARANYA! NO 8-10

Answer 1

Soal (8) 
y = 2 sin ( 2x - 20 )
y' = 2 cos ( 2x - 20 ) . (2)
= 4 cos ( 2x - 20 ) ---> y minimum jika y' = 0
4 cos ( 2x - 20 ) = 0

cos ( 2x - 20 ) = 0
cos ( 2x - 20 ) = cos 270
2x - 20 = 270
2x = 290
x = 145 ---> jawaban : D

Soal (10)
y = 3 cos ( 2x - 30 )
y' = -3 sin ( 2x - 30 ) . (2)
= -6 sin ( 2x - 30 ) ---> y minimum jika y' = 0
-6 sin ( 2x - 30 ) = 0

sin ( 2x - 30 ) = 0
sin ( 2x - 30 ) = sin 180
2x - 30 = 180
2x = 210
x = 105 

y = 3 cos ( 2x - 30 )
= 3 cos [ 210 - 30 ]
= 3 cos 180
= 3 (-1)
= -3
Titik minimum = ( 105, -3 )---> jawaban : D
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