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If A + C = 2B, then cosC-cosAsinA-sinC is equal to ______.

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Question

If A + C = 2B, then `(cos C - cos A)/(sin A - sin C)` is equal to ______.

Options

  • cot B

  • cot 2B

  • tan 2B

  • tan B

MCQ
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Solution

If A + C = 2B, then `(cos C - cos A)/(sin A - sin C)` is equal to tan B.

Explanation:

`(cos C - cos A)/(sin A - sin C)`

= `(2 sin ((A + C)/2) sin ((A - C)/2))/(2 cos ((A + C)/2) sin((A - C)/2)`

= `(2 sin B)/(2 cos B)`  ...[∵ A + C = 2B]

= tan B   

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Conversion Formulae in Trigonometry
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