快遞百科

標題:

F.4 Maths

發問:

Consider △ABC,where sinA:sinB:sinC=2:3:4 and A=29°.If the perimeter of △ABC is 108cm,solve △ABC.

最佳解答:

Let 3 sides of △ABC be a , b , c : By sine formula : a : b : c = sinA:sinB:sinC = 2:3:4 The perimeter of △ABC is 108cm , so a + b + c = 108 So a = 108 * 2/(2+3+4) = 24cm b = 24 * 3/2 = 36cm c = 24 * 4/2 = 48cm ; sinA : sinB = a : b sin 29 : sinB = 24 : 36 sinB = (sin29) * 36/24 B = 46.653375° C = 180 - 29 - 46.6553375 = 104.3466°

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