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If A=30^(@), then prove that : " ...

If `A=30^(@)`, then prove that :
`" "cos3A=4cos^(3)A-3cosA`

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ICSE-TRIGONOMETRICAL RATIOS OF STANDARD ANGLES-EXERCISE 23(C)
  1. If A=30^(@), then prove that : " "cos3A=4cos^(3)A-3cosA

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  2. Solve the following equations for A, if : 2sinA=1

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  3. Solve the following equations for A, if : 2cos2A=1

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  4. Solve the following equations for A, if : sin3A=sqrt(3)/2

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  5. Solve the following equations for A, if : sec2A=2

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  6. Solve the following equations for A, if : sqrt(3)tanA=1

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  7. Solve the following equations for A, if : tan3A=1

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  8. Solve the following equations for A, if : 2sin3A=1

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  9. Solve the following equations for A, if : sqrt(3)cot2A=1

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  10. Calculate the value of A, if : (sinA-1)(2cosA-1)=0

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  11. Calculate the value of A, if : (tanA-1)(cosec3A-1)=0

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  12. Calculate the value of A, if : (sec2A-1)(cosec3A-1)=0

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  13. Calculate the value of A, if : cos3A.(2sin2A-1)=0

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  14. Calculate the value of A, if : (cosec2A-2)(cot3A-1)=0

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  15. If 2sinx^(@)-1=0 and x^(@) is an acute angle, find: (i) bsinx^(@)" ...

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  16. If 4cos^(2)x^(@)-1=0 and 0 le x^(@) le 90^(@), find : x^(@)

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  17. If 4cos^(2)x^(@)-1=0 and 0 le x^(@) le 90^(@), find : sin^(2)x^(@)+c...

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  18. If 4cos^(2)x^(@)-1=0 and 0 le x^(@) le 90^(@), find : 1/(cos^(2)x^(@...

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  19. If 4sin^(2)theta-1=0 and angle theta is less than 90^(@), find the val...

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  20. If sin3A=1 and 0 le A le 90^(@), find : sin A

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  21. If sin3A=1 and 0 le A le 90^(@), find : cos 2A

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