4 years ago

Find the value of cos(20) using double-angle formula given: 20 points !!! I need help ASAP

Mathematics

1 answer:

MissTica4 years ago

3 0

the correct answer is -1/9

explanation

cos(2A)

=cos(A+A)

=cosA.cosA - sinA.sinA

=cos ^2A- sin^2A

=cos^2A - 1 + cos^2A

=2cos^2A-1

putting the value of cos A -2/3

2*(-2/3)^2-1

=2*4/9-1

=8/9-1

=-1/9

here is put theta as A because I don't find theta symbol

don't forget to mark as brainllest answer

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