Question

korzystając ze wzoru:

cos (180⁰ - α) = - cos α

oblicz :

*cos 120 ⁰

*coś 150 ⁰

*cos 135 ⁰

*cos 180 ⁰

Prosze o pełne rozwiązania

Dzieki z góry. :)

Answer 1

cos ( 180⁰ - α ) = - cos α

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cos 120⁰ = cos (180⁰ - 60⁰) = - cos 60⁰ = - 1/2

cos 150⁰ = cos ( 180⁰ - 30⁰ ) = - cos 30⁰ = - √3/2

cos 135⁰ = cos (180⁰ - 45⁰ ) = - cos 45⁰ = - √2/2

cos 180⁰ = cos ( 180⁰ - 0⁰ ) = - cos 0⁰ = - 1

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