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张角公式 如图 1,设点C在线段AB上 ,AB外一点P对线段AC、BC的张角分别为γ、β ,则sin(γ + β)PC =sinγPB + sinβPA .证明 由SΔPAB =SΔPAC +SΔPBC 得图 112 PA·PBsin(γ + β) =12 PA·PCsinγ+ 12 PB·PCsinβ两边同除以 12 PA·PB·PC得sin(γ+ β)PC =sinγPB + si
The opening angle formula is shown in Fig.1. Suppose point C is on line segment AB, and the external angles of AB to the line segments AC and BC are γ and β, then sin (γ + β) PC = sinγPB + sinβPA. SΔPAC + SΔPBC Figure 112 PA · PBsin (γ + β) = 12 PA · PCsinγ + 12 PB · PCsinβ divided by 12 PA · PB · PC sin (γ + β) PC = sinγPB + si