mayadevimaharjan88 mayadevimaharjan88
  • 02-07-2020
  • Mathematics
contestada

if cos2A=11/25, show that cosA=6/5√2​

Respuesta :

tonb
tonb tonb
  • 02-07-2020

Answer:

it is not I think...

Step-by-step explanation:

Using the identity

[tex]\cos(2a) = 2 \cos^2(a) - 1[/tex]

We can solve:

[tex]2 \cos^2(a) - 1 = \frac{11}{25}[/tex]

[tex]2 \cos^2(a) = \frac{36}{25}[/tex]

[tex]\cos^2(a) = \frac{18}{25}[/tex]

[tex]\cos(a) = \sqrt \frac{18}{25}[/tex]

[tex]\cos(a) = \sqrt{ 2 \cdot \frac{3^2}{5^2} }= \frac35 \sqrt 2[/tex]

So whoever asked the question forgot the factor 2!!!

Or did I miss anything??

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