Question

value of cos 43.5 degrees ??
​

Answer 1

Step-by-step explanation:

We have: sin

−1

(cos

5

53π

)

=sin

−1

(cos

5

50π+3π

)

=sin

−1

(cos(

5

50π

+

5

3π

))

=sin

−1

(cos(10π+

5

3π

))

=sin

−1

(cos(

5

3π

)), [∵cos(2nπ+θ)=cosθ,n∈Z]

=sin

−1

(sin(

2

π

−

5

3π

)), [∵sin(

2

π

−θ)=cosθ]

=sin

−1

(sin(−

10

π

))=−

10

π

Note sin

−1

(sinθ)=θ if −

2

π

≤θ≤

2

π

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