Anonymous

sinα = ⅘ cosα = √(1-sin²α) = ⅗ cosβ = -5/13 sinβ = √(1-cos²β) = 12/13 cos(α-β) = cosα·cosβ + sinα·sinβ = ⅗(-5/13) + ⅘(12/13) = -15/65 + 48/65 = 33/65

Anonymous

Rule cos(α-β)=cosαcosβ+sinαsinβ

Anonymous

sin(β ) = 12/13 and cos(α) = 3/5 cos(α - β) = cos(α)cos(β) + sin(α)sin(β) = (3/5)(-5/13) + (4/5)(12/13) = -15/65 + 48/65 = 33/65

Anonymous

1. cosα? Quadrant I means positive coseno cosα=√(1-sin²α)=√(1-16/25)=√(9/25)=3/5 2. sinβ? Quadrant II means positive seno sinβ=√(1-cos²β)=√(1-25/169)= =√(144/169)=12/13 3. cos(α-β)=cosαcosβ+sinαsinβ= =(3/5)*(-5/13)+(4/5)*(12/13)= 33/65