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If sin alpha =4/5 where alpha is a posit...

If `sin alpha =4/5` where `alpha` is a positive acute angle then cos `alpha`=

A

`3/5`

B

`-3/5`

C

`pm3/5`

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
C
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CHHAYA PUBLICATION-TRIGONOMETRIC RATIOS [OR FUNCTIONS] OF POSITIVE ACUTE ANGLES-EXERCISE 2
  1. The minimum value of sin theta.cos theta is

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  2. If 0lttheta lt90^@ then minimum value of 9tan^2theta+4cot^2theta is

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  3. If sin alpha =4/5 where alpha is a positive acute angle then cos alpha...

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  4. If x=sin^2alpha+cosec^2alpha , state which of the following is true?

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  5. If tan theta=a/b ,then which of the following is the value of (asin th...

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  6. If 0^@le A le90^@ and sin A =cosA , state which of the following is t...

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  7. State which of the following relation is true?

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  8. Prove the following identities: sin A cos A (tanA+cotA)=1

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  9. Prove the following identities: sinalpha cosalpha(tanalpha-cotalpha...

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  10. Prove the following identities: sqrt((1+sintheta)/(1-sin theta))=sec...

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  11. Prove the following identities: sqrt((cosectheta-1)/(cosec+1))=(1-si...

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  12. Prove the following identities: (cosphi)/(1+sinphi)+(1+sinphi)/(cos ...

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  13. Prove the following identities: (cosec theta-sintheta)^2+(sectheta-c...

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  14. Prove the following identities: (cottheta+cosectheta)^2=(1+costheta)...

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  15. Prove the following identities: (1+sintheta)/(1-sintheta)=(sectheta+...

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  16. Prove the following identities: (sinalpha+cosecalpha)^2+(cosalpha+se...

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  17. Prove the following identities: (1+secA+tanA)(1-cosecA+cotA)=2

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  18. prove: ((sin0^@+sin60^@)(cos60^@+cot45^@))/((cot60^@+tan30^@)(cosec30^...

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  19. prove: cos^2 ""60^@,cos^2 ""45^@,cos^2 ""30^@ are in A.P

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  20. prove: tan(pi/3),tan(pi/4),tan(pi/6) are in G.P

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