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If 4 cos^(2) A - 3 = 0, show that : ...

If
`4 cos^(2) A - 3 = 0,`
show that :
`cos 3 A = 4 cos^(3) A - 3 cos A`

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ICSE-TRIGONOMETRICAL IDENTITIES-EXERCISE 21 (E)
  1. Prove that : (cos A)/(1 + sin A) = sec A - tan A

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  2. Prove that : cos A (1 + cot A) + sin A (1 + tan A) = sec A + cosec A

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  3. Prove that : (sin A - cos A) (1 + tan A + cot A) = (sec A)/ (cosec^(...

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  4. Prove that : sqrt (sec^(2) A + cosec^(2) A) = tan A + cot A

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  5. Prove that : (sin A + cos A) (sec A + cosec A) = 2 + sec A cosec A

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  6. Prove that : (tan A + cot A) (cosec A - sin A) (sec A - cos A) = 1

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  7. Prove that : cot^(2) A - cot^(2) B = (cos^(2) A - cos^(2) B)/ (sin^(...

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  8. Prove that : (cot A - 1)/ (2 - sec^(2) A) = (cot A)/ (1 + tan A)

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  9. If 4 cos^(2) A - 3 = 0 and 0^(@) le A le 90^(@), then prove that :...

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  10. If 4 cos^(2) A - 3 = 0, show that : cos 3 A = 4 cos^(3) A - 3 co...

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  11. Find A, if 0^(@) le A le 90^(@) and : 2 cos^(2) A - 1 = 0

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  12. Find A, if 0^(@) le A le 90^(@) and : sin 3 A - 1 = 0

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  13. Find A, if 0^(@) le A le 90^(@) and : 4 sin^(2) A - 3 = 0

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  14. Find A, if 0^(@) le A le 90^(@) and : cos^(2) A - cos A = 0

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  15. Find A, if 0^(@) le A le 90^(@) and : 2 cos^(2) A + cos A - 1 = ...

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  16. If 0^(@) le A le 90^(@), find A, if : (cos A)/ (1 - sin A) + (co...

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  17. If 0^(@) le A le 90^(@), find A, if : (sin A)/ (sec A - 1) + (si...

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  18. Prove that : (cosec A - sin A) (sec A - cos A) sec^(2) A = tan A

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  19. Prove the identity ("sin"theta+"cos"theta)("tan"theta+"cot"theta)="s...

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  20. Evaluate without using triignometric tables,** "sin"^(2)28^(@)+"sin...

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