Bantu dijawab. Jawaban terbaik akan saya jadikan sebagai jawaban tercerdas.
RanshiVM
A. cosxcos20° - sinxsin20° = 1/2 cos(x + 20°) = 1/2 cos(x + 20°) = cos60° x + 20° = 60° + k . 360° x = 40° + k . 360° x = 40° x + 20° = -60° + k . 360° x = -80° + k . 360° x = 280° HP = {40°, 280°}
b. sin100°cos2x - cos100°sin2x = -1/2 sin(100° - 2x) = -1/2 sin(100° - 2x) = sin330° 100° - 2x = 330° + k . 360° -2x = 230° + k . 360° x = -115° - k . 360° x = 245° 100° - 2x = (180° - 330°) + k . 360° -2x = -150° + k . 360° x = 75° - k . 360° x = 75° HP = {75°, 245°}
c. (tan1/2x - tan50°)/(1 + tan1/2xtan50°) = -1 tan(1/2x - 50°) = -1 tan(1/2x - 50°) = tan135° 1/2x - 50° = 135° + k . 180° 1/2x = 185° + k . 180° x = 370° + k . 360° x = 10° HP = {10°}
RanshiVM
Iya, sama-sama. Btw perlu digarisbawahi, jika sudah mengenai trigonometri kita harus hafal rumus-rumusnya. Kalau sudah hafal dan paham, insyaAllah bisa lancar mengerjakan :)
cos(x + 20°) = 1/2
cos(x + 20°) = cos60°
x + 20° = 60° + k . 360°
x = 40° + k . 360°
x = 40°
x + 20° = -60° + k . 360°
x = -80° + k . 360°
x = 280°
HP = {40°, 280°}
b. sin100°cos2x - cos100°sin2x = -1/2
sin(100° - 2x) = -1/2
sin(100° - 2x) = sin330°
100° - 2x = 330° + k . 360°
-2x = 230° + k . 360°
x = -115° - k . 360°
x = 245°
100° - 2x = (180° - 330°) + k . 360°
-2x = -150° + k . 360°
x = 75° - k . 360°
x = 75°
HP = {75°, 245°}
c. (tan1/2x - tan50°)/(1 + tan1/2xtan50°) = -1
tan(1/2x - 50°) = -1
tan(1/2x - 50°) = tan135°
1/2x - 50° = 135° + k . 180°
1/2x = 185° + k . 180°
x = 370° + k . 360°
x = 10°
HP = {10°}
Semoga membantu