mohon djwb kumpulin besok

berusahalah mengerjakan sendiri terlebih dulu sebelum meminta bantuan.

1.) cos 75° = cos (30° + 45°)
cos 75° = (cos 30°.cos 45°) - (sin 30°.sin 45°)
cos 75° = (1/2√3)(1/2.√2) - (1/2)(1/2.√2)
cos 75° = (1/4.√6) - (1/4√2)
cos 75° = 1/4 (√6 - √2)

2.) sin 300 = sin (360-300)
= - sin 60
= - 1/2 √3

3.) -2 - √3 (D)

4.) cos(90-a) = √3 cos a
sin a = √3 cos a
sin a/cos a = √3
tan a = √3 (D)

5.) tan A = y/x = 2/3
x = 3
y = 2
r = √x² + y²
r = √3² + 2²
r = √9 + 4
r = √13

sin A = y/r
= 2/√13
= 2/13 √13

cos A = x/r
= 3/√13
= 3/13 √13

sin 2A = 2 sin A. cos A
= 2 (2/13 √13)(3/13 √13)
= 156/169
= 12/13

7.) sin a = 3/5 , maka cos a = 4/5

karna di kuadran II cos bernilai negatif sehingga cos a = 4/5

maka :
sin 2a = 2 sin a cos a
= 2 (3/5) (4/5)
= 24/25

8.) sin a = 3/5, cos a = 4/5
sin b = 7/25 , maka cos a = 24/25

cos (a-b) = cosAcosB + sinAsinB
= 4/5 × 24/25 + 3/5 × 7/5
= 96/125 + 21/125
= 117/125