# Precalc

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If α, β, and γ are direction angles for a vector in three dimensions and cos α = 0.6 and cos β = 0.7, find cos γ

• Precalc -

recall that

cos2α + cos2β + cos2γ = 1

.36 + .49 + cos2γ = 1
cos2γ = .15
cosγ = 0.38

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