Question

23. If sinA + sinA = 1, then find cos A +cos'A.​

Answer 1

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✒Given :

⟶sinØ+ sin²2Ø =1.

✒To find :-

⟶ cos² Ø + cos4 Ø.

✒ Solution :-

We have,

°. sinØ + sin²Ø = 1

⟹ sin Ø = 1 - sin²Ø

⟹ sin Ø = cos² Ø

[ Squaring both side ]

⟹ sin²Ø = cos4Ø ____________(i).

✒Now,

°° cos²Ø + cos4 Ø

⟹ cos²Ø + sin²Ø ______________ [Using (i)].

⟹ 1

[sin²Ø + cos²Ø = 1]

proved.