Angle addition formulas express trigonometric functions of sums of angles alpha+/-beta in terms of functions of alpha and beta. The fundamental formulas of angle addition in trigonometry are given by sin(alpha+beta) = sinalphacosbeta+sinbetacosalpha (1) sin(alpha-beta) = sinalphacosbeta-sinbetacosalpha (2) cos(alpha+beta) = cosalphacosbeta-sinalphasinbeta (3) cos(alpha-beta) = cosalphacosbeta+sinalphasinbeta (4) tan(alpha+beta) = (tanalpha+tanbeta)/(1-tanalphatanbeta) (5)
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