Question

Tolong bantu ya.. terimakasih :)

Answer 1

AB = BC => AC = 2BC
Sudut CBD = a

Tan a = DC/BC => DC = BC Tan a

AD = √(AC^2 + DC^2)
AD = √( (2BC)^2 + (BC Tan a)^2)
AD = √(4BC^2 + BC^2 tan^2 a)
AD = √(BC^2(4 + tan^2 a))
AD = BC √(4 + tan^2 a)

Cos CAD = AC/AD = (2BC)/(BC√(4 + tan^2 a)) = 2/√(4 + tan^2 a) .. D