1. sin 2x = cos (x+15) 2. 2sin^2x +sinx-1=0 3. cos^2x + sin (90+x) -2 = 0 4. 3 tan^2+ 5 tanx - 2 mohon bantuannnyaaa

Persamaan trigonometri

1. sin 2x = cos (x + 15)
sin (2x) = sin { 90 - (x +15)}
2x = 90 - x - 15
3x = 75
x = 25

2.
2 sin² x + sin x  - 1= 0
(2 sin x - 1)(sinx + 1) = 0
2 sin x - 1 = 0  atau sin x + 1 = 0
sin x = 1/2  atau sin x = -1
.
sin x = 1/2 = sin 30 = sin 150
x = 30, 150
sin x = 1 = sin 270
x = 270
HP x = (30, 150, 270)

3.
cos² x + sin(90 + x)  - 2 = 0
cos² x + cos x - 2 = 0
(cos x -1)(cos x + 2) = 0
cos x - 1= 0 atau cos x + 2 = 0
cos x =  1   atau cos x = - 2 (TM)

cos x = 1 = cos 90
x = 0

4.
3 tan² x  + 5 tan x - 2= 0
(3tan x -1) ( tan x  + 2) = 0
tan x = 1/3    atau tan x = - 2