prove cos(2x-40)=0.8

Solution

prove

cos (2 x - 40) = 0.8

False

Solution steps

cos (2 x - 40) = 0.8

Show that the two sides are not equal

For

cos (2 x - 40) = 0.8

plug in

x = 0

cos (2 \cdot 0 - 40) = - 0.66693 \dots

cos (2 \cdot 0 - 40)

Refine to a decimal form

= - 0.66693 \dots

The two sides are not equal

\Rightarrow False

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