cosθ = sin(a) What is a?
a = π/2 - θ or a= θ + π/2 so cosθ = sin(π/2 - θ) = sin(θ + π/2)
If sinθ=cosa, what is a?
a=π/2 - θ or a= θ - π/2 so sinθ = cos(π/2 - θ) = cos(θ - π/2)
cos(θ + π/2)
-sinθ
sin(θ - π/2)
-cosθ
sin(π/6)
1/2
sin(π/4)
1/√2
sin(π/3)
√3 / 2
cos(π/3)
1/2
cos(π/4)
1/√2
cos(π/6)
√3 / 2
Law of cosines
b2 = a2 + c2 - 2ac cosβ

