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Question
Select the correct option from the given alternatives:
In ΔABC if c2 + a2 – b2 = ac, then ∠B = ____.
Options
`π/4`
`π/3`
`π/2`
`π/6`
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Solution
In ΔABC if c2 + a2 – b2 = ac, then ∠B = `underlinebb(π/3)`.
Explanation:
cos B = `(c^2 + a^2 - b^2)/(2ac)`
cos B = `(ac)/(2ac)`
cos B = `1/2`
cos B = cos `pi/3`
B = `pi/3`
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