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  1. The numerical value of cot18°
    is
    1. 1
    2. √2
    3. 3
    4. 1
      √3
Correct Option: A

cot 18°

cot72° . cos²22° +
1
tan 72° . sec²68°

= cot 18°.cot 72°.cos²22° +
cot 18°
= cot 18°.tan 18°.cos²22° +
cot 18°
. cos² 68°
tan 72° . sec² 18°cot 18°

= cos² 22°+ cos² 68°
= cos²22° + sin²22° = 1


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