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If cos, 25^0 +sin , 25^0=k, then cos, 20^0 is equal to

Question

If $cos 2 5^{0} + s in 2 5^{0} = k$ , then $cos 2 0^{0}$ is equal to

\frac{k}{2}

- \frac{k}{2}

\pm \frac{k}{2}

none of these

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cos 2 5^{0} + s in 2 5^{0} = k

, then

cos 2 0^{0}

is equal to

13 mins ago

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13 mins ago

Text solutionVerified

cos 2 5^{\circ} + sin 2 5^{\circ} = k

\frac{1}{2} cos 2 5^{\circ} + \frac{1}{2} sin 2 5^{\circ} = \frac{k}{2}

sin (4 5^{\circ} + 2 5^{\circ}) = \frac{k}{2}

sin 7 0^{\circ} = \frac{k}{2}

sin (9 0^{\circ} - 2 0^{\circ}) = \frac{k}{2}

cos 2 0^{\circ} = \frac{k}{2}

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Question Text	If $cos 2 5^{0} + s in 2 5^{0} = k$ , then $cos 2 0^{0}$ is equal to
Answer Type	Text solution:1
Upvotes	150