tolong dong yg mana saja terserah 1 no juga gak papa

jawab
1. sin A = 8/17, cos A = - 15/17, tan A = -8/15
cos B = 3/5 , sin B = 4/5, tan B = 3/4
a. cos (A-B) = cos A cos B + sin A sin B = (-15/17)(3/5) + (8/17)(4/5)
= (-45+32)/85 = - 13/85
b. tan (A+B)= (tan A + tan B) / (1 - tan A tan B)
= (-8/15 + 3/4)  / ( 1 - (-8/15)(3/4)
= (-32 + 45) / (60 + 24)
=  - 13/84

2. sin A= - 5/13
cos² A =  1- (-5/13)² = 1- 25/169 = 144/169
cos A = - 12/13
sin 2A = 2 sin A cos A = 2(-5/13)(-12/13) = 120/169

5. 4 sin 105 cos 15 =
= 2 ( 2 sin 105 cos 15)
= 2 { sin(105 +15) + sin (105 - 15)}
= 2 (sin 120 + sin 90)
= 2 ( sin 60 + sin 90)
= 2 ( 1/2 √3 + 1)
= √3  + 2
= 2 + √3