Mohon dibantu yaa :) besok dikumpul :) please!!! tolongin dede kak!!! bantuin dong :

sin x = 4/5
(cos x)^2 = 1 - (sin x)^2
(cos x)^2 = 1 - (4/5)^2
(cos x)^2 = 1 - 16/25
(cos x)^2 = 9/25
cos x = √(9/25) = 3/5
cos 2x = 2cos^2 x -1
= 2(3/5)^2 - 1
= 18/25 - 1
= - 7/25
sin 2x = 2sin x cos x
= 2.(4/5)(3/5)
= 24/25
tan 2x = sin 2x / cos 2x
= (24/25)/(-7/25)
= -24/7
2) tan a = 1/2
tan 2a = 2 tan a /(1-tan^2 a)
= 2.1/2 /(1 - 1/2^2)
= 1 / (1-1/4)
= 1 / (3/4)
= 4/3
tan b = 1/3
tan 2b = 2tan b /(1-tan^2 b)
= 2.1/3 /(1- 1/3^2)
= 2/3 / (1 - 1/9)
= 2/3 /(8/9)
= 3/4
3) tan b = 3/4
tan 2b = 2tan b /(1-tan^2 b)
= 2.3/4 /(1-3/4^2)
= 6/4/(1-9/16)
= 3/2(7/16)
= 21/32
tan 4b = 2tan 2b / (1- tan^2 2b)
= 2.21/34 /(1-21/34^2)
= 42/34 /(1- silahkan lanjutkan...!