Page 17 - E-MODUL MATEMATIKA 1

TRIGONOMETRI 1 16

2. Buktikan bahwa cos ( ) + cos ( ) = cos a
Bukti :

Ruas kiri = cos ( ) + cos ( )

=( cos cos a – sin sin a ) + ( cos cos a + sin sin a )

= 2 cos cos a

= 2( ) cos a

= cos a
= Ruas kanan (terbukti)
0
3. Hitung nilai Sin 75 tanpa menggunakan kalkulator atau tabel
matematika Jawab : 0
0
0
Sin 75 = Sin(45 + 30 )
0
0
0
0
= sin 45 cos 30 + cos 45 sin 30
= ( )( )+( )( )

= +

= ( + )

4. Diketahui sin A = ,cos B = ,sudut A dan B lancip.Hitunglah nilai
tan( A – B )!
Jawab :

AP =
=
=
= = 4 tan A =

RS =
=
=
= = 5 tan B =

Tan (A – B ) =

=

=

= x
=