nilai dari sec 285 adalah?

Materi : Trigonometri

Pembahasan :
Sin 15°
= Sin (45° - 30°)
= Sin 45° . Cos 30° - Cos 45° Sin 30°
= (1/2√2)(1/2√3) - (1/2√2)(1/2)
= 1/4√6 - 1/4√2
= 1/4(√6 - √2)

Sec 285°
= 1/Cos 285°
= 1/Cos (270 + 15)°
= 1/Sin 15°
= 1/[1/4(√6 - √2)
= 4/(√6 - √2)
= 4/(√6 - √2) . (√6 + √2)/(√6 + √2)
= (4√6 + 4√2)/(6 - 2)
= √6 + √2