Side B C of a triangle A B C has been pr...

Side `B C` of a triangle `A B C` has been produced to a point `D` such that `/_120^0dot` If `/_B=1/2/_A ,` then `/_A` is equal to `80^0` (b) `75^0` (c) `60^0` (d) `90^0`

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In `/_\ABC
/_ACD = /_A+ /_B
120@=2/_B + /_B
120@ = 3 /_B
/_B=120/3
/_B = 40@`
Also, `/_A = 2/_B`
`/_A = 2 (40@)`
= `80@`
Thus,` /_A = 80@`.

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