How do you use the angle sum identity to find the exact value of cos 105?

Litzy Downs 2022-09-30 Answered
How do you use the angle sum identity to find the exact value of cos 105?
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Answers (2)

Dayana Powers
Answered 2022-10-01 Author has 6 answers
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cos ( a + b ) = cos a cos b sin a sin b
Therefore,
cos 105 = cos ( 60 + 45 )
= cos 60 cos 45 sin 60 sin 45
= ( 1 2 ) × ( 2 2 ) ( 3 2 ) × ( 2 2 )
= 1 4 ( 2 6 )
0.2588
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Vrbljanovwu
Answered 2022-10-02 Author has 2 answers
using the trigonometric identity
cos ( x + y ) = cos x cos y sin x sin y
cos 105 = cos ( 60 + 45 )
= cos 60 cos 45 sin 60 sin 45
= ( 1 2 × 2 2 ) ( 3 2 × 2 2 )
= 2 4 6 4 = 1 4 ( 2 6 )
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