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Express cos40^@ cos80^@ in sum form...

Express `cos40^@ cos80^@` in sum form

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`1/2(cos120^@+cos40^@)`
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A N EXCEL PUBLICATION-TRIGONOMETRIC FUNCTIONS-QUESTION BANK
  1. Express sintheta+sin3theta and sin5theta+sin7theta in product form

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  2. Prove that sintheta+sin3theta+sin5theta+sin7theta=4costhetacos2thetasi...

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  3. Express cos40^@ cos80^@ in sum form

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  4. Prove that cos20^@ cos40^@ cos80^@=1/8

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  5. Express sin3A and cos2A in terms of sine function

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  6. Convert sin5A+sinA into product form and show that sin5A=5sinA-20sin^3...

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  7. If A=18^@ deduce the value of sin36^@=sqrt(10-2sqrt5)/4

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  8. Prove that cos^2theta=(1+cos2theta)/2

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  9. Evaluate cos^2(pi/8)+cos^2((3pi)/8)

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  10. Evaluate cos^2(pi/8)+cos^2((3pi)/8)+cos^2((5pi)/8)+cos^2((7pi)/8)=2

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  11. Prove that sinA/(1+cosA)=tan(A/2)

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  12. Show that tan 15^@ = 2 - sqrt3

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  13. Given that 1-costheta=2sin^2(theta/2) and 1+costheta=2cos^2(theta/2) p...

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  14. Given that 1-costheta=2sin^2(theta/2) and 1+costheta=2cos^2(theta/2)de...

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  15. Writing 4A=2xx2A prove that sin4A=4sinAcos^3A-4cosAsin^3A

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  16. if sin4A=4sinAcos^3A-4cosAsin^3A Dividing numerator and denominator on...

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  17. cosecA=1/sinA and cotA=cosA/sinA prove cosecA-cotA=tan(A/2)

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  18. Given that 1-costheta=2sin^2(theta/2) and 1+costheta=2cos^2(theta/2)de...

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  19. Given that tantheta=a/b find sin2theta and cos2theta

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  20. Given that tantheta=a/b prove that bcos2theta+asin2theta=b

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