1.

If a = 7 , b= 3, c=5 then find A.

Answer»

SOLUTION :If a = 7 , B= 3, c=5 then
cosA = `(b^2 + c^2 + a^2)/(2bc) = (9 + 25 - 49)/(2 xx 3 xx 5) = (-15)/(2xx3xx5) = -1/2`
`THEREFORE` cosA = -1/2 or A = `120^@`


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