Jika sin a= 1/2, tentukan: 1. cos (180-a) + 3sin (90+a) - 4cos (270-a) + cos (360-a) =... 2. sin (180+a) - 5cos (270+a) + 3sin (90+a) - 4cos (180-a) =...

<p>Diketahui sin α = 1/2<br>dari sini bisa kita ketahiu bahwasanya α = 30° dan cos α = √3/2</p><p>&nbsp;</p><p>&nbsp;</p><p><strong>No.1</strong><br>cos (180°-α) + 3sin (90°+α) - 4cos (270°-α) + cos (360°-α) =...</p><p>&nbsp;</p><ul><li><strong>Langkah pertama yaitu menggunakan Identitas Trigonometri</strong><br>cos (180°−α) = −cos α<br>sin (90°+α) = cos α<br>cos (270°−α) = −sin α<br>cos (360°−α) = cos α</li><li><strong>Kemudian masukkan pada soal!</strong><br>(−cos α) + 3(cos α) - 4(-sin α) + (cos α)</li><li><strong>lalu gabungkan agar terlihat lebih mudah!</strong><br>= (−cos α + 3cos α + cos α) + 4 sin α<br>= 3 cos α + 4 sin α</li><li><strong>langkah terakhir, masukkan nilai!</strong><br>= 3 (√3/2) + 4 (1/2)<br>= 2√3/2 + 2<br>------------------<br>| &nbsp; &nbsp;2 + 2√3/2 &nbsp; &nbsp;|<br>------------------</li></ul><p>&nbsp;</p><p>&nbsp;</p><p><strong>No. 2</strong><br>sin (180°+α) - 5cos (270°+α) + &nbsp;3sin (90°+α) - 4cos (180°-α) =...</p><p>&nbsp;</p><ul><li><strong>Sama seperti no. 1 menggunakan Identitas Trigonometri:</strong><br>sin (180°+α) = -sin α<br>cos (270°+α) = sin α<br>sin (90°+α) = cos α<br>cos (180°-α) = -cos α</li><li><strong>Gabungkan!</strong><br>= -6 sin α + 7 cos α</li><li><strong>Masukkan nilai!</strong><br>= -6 (1/2) + 7 (√3/2)<br>= -3 + 7√3/2<br>------------------<br>| &nbsp; &nbsp;7√3/2 -3 &nbsp; &nbsp; &nbsp;|<br>------------------<br>&nbsp;</li></ul>