Question

1. (1-Cos²α)Cot² equivalen dengan...

2. nilai dari sin 45×cos 120-cos 135×cos 150 adalah

Answer 1

1. (1 - cos^2 α).cot^2 α
= sin^2 α.(cos^2 α/sin^2 α)
= cos^2 α

2. sin 45×cos 120 - cos 135×cos 150
= 1/2√2×cos (180-60) - cos (180-45)×cos (180-30)
= 1/2√2×(- cos 60) - (- cos 45)×(- cos 30)
= 1/2√2×(-1/2) - (-1/2√2)×(-1/2√3)
= -1/4√2 - 1/4√6
= -1/4√2.(1 + √3)