How do you provle $cos (π - x) = - cos x$ $cos (pi-x) =- cosx$ ?

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How do you provle $cos (π - x) = - cos x$ $cos (pi-x) =- cosx$ ?

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Answer 1 · 2016-01-30T12:18:57

see explanation

Explanation:

using the trig formula: cos(x-y) =cosxcosy + sinxsiny

hence $cos (π - x) = cos π cos x + sin π sin x$ $cos (pi - x) = cospicosx + sinpisinx$

now $cos π = - 1, sin π = 0$ $cospi = -1 , sinpi = 0$

then $cos (π - x) = - 1 cos x + 0 = - cos x$ $cos(pi - x ) = -1 cosx + 0 = -cosx$

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How do you provle $cos (π - x) = - cos x$ $cos (pi-x) =- cosx$ ?

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How do you provle cos(π−x)=−cosxcos (pi-x) =- cosx?

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How do you provle $cos (π - x) = - cos x$ $cos (pi-x) =- cosx$ ?