nilai dari sin 127,5 derajat

jawab

sin A = √( 1 /2  - 1/2 cos 2A)

sin 127,5 = √ (1/2)(1  - co s255)

= √ (1/2)(1 - sin 15)

= √ (1/2 ( 1 - 1/4 (√6 - √2))

= √ ( 1/2)(1 - 1/4 √6 + 1/4 √2)

= √ (1/2)(1/2) ( 1 - 1/2 √6+ 1/2√2)
= 1/2 √( 1/4 ( 4 - 2√6 + 2 √2)
= 1/4  √(4 - 2√6 + 2√2)