Q7 of 268 Page 5

If cos55° = x2, then write the value of sin 55o in terms of x.

We know that

cos2 θ + sin2 θ = 1


⇒ cos2 55° + sin2 55° = 1


⇒ sin2 55° = 1 – cos2 55°


⇒ sin 55° = √(1 – cos2 55°)


And Given that cos 55° = x2


⇒ sin 55° = √{1– (x2)2}


⇒ sin 55° = √(1 – x4)


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