Question

Tolong ya kak pake caranya

Answer 1

Verified answer

Jawab
a.  sifat 1 - 2 sin² x = cos 2x
2 - 4 sin² 112,5 =  2 (1 - 2 sin² 112,5)
= 2  cos 2(112,5)
= 2 cos (225)
= 2 cos( 180 + 45)
= 2 (- cos 45)
= 2 ( -1/2 √2)
= - √2

b. sifat tan 2x = 2 tan  x/ (1 -tan x)(1 + tanx)

{ 2 tan 67,5) / (1 - tan 67,5)(1 + tan 67,5) = tan 2(67.5)
= tan 135
= tan (180 -45)
= - tan 45
= -1

c.  sifat  2 sin A cos A = sin 2 (A)
10 sin 78,75  cos 78,75 =
= 5 ( 2 sin 78,75 cos 78,75)
= 5 sin 2(78,75)
= 5 sin 157,5
= 5 sin (180 - 157,5)
= 5 sin 22,5
= 5 {√ ( 1/2 - 1/2 cos 45}
= 5 {√ (1/2 - 1/4 √2)
= 5 { √ 1/4 (2 - √2)
= (5/2) √ (2 - √2)