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Prove that cos420^@ sin390^@+cos(-300^@)...

Prove that `cos420^@ sin390^@+cos(-300^@)sin(450^@)=3/4`

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A N EXCEL PUBLICATION-TRIGONOMETRIC FUNCTIONS-QUESTION BANK
  1. Complete the following and find the value of a1 , a2. . . a7 and b1 , ...

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  2. Prove that sin120^@ cos330^@ +cos240^@ sin330^@=1

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  3. Prove that cos420^@ sin390^@+cos(-300^@)sin(450^@)=3/4

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  4. Prove that sin^2(theta-phi)-sin^2(theta+phi)= -sin2theta sin2phi hence...

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  5. Given that tan(A+B)=(tanA+tanB)/(1-tanAtanB) by writing A+B+C=(A+B)+C...

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  6. Given that tan(A+B)=(tanA+tanB)/(1-tanAtanB) if A+B+C=0^@ prove that t...

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  7. Prove that sin(A+B)sin(A-B)=sin^2A-sin^2B

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  8. Given that sin18^@=(sqrt5-1)/4 prove thatsin^2 24^@-sin^2 6^@=(sqrt5-1...

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  9. Express sinA+sin3A and cosA+cos3A in product form

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  10. Prove that (sinx+sin3x)/(cosx+cos3x)=tan2x

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  11. If A=30^@ deduce the value of tan60^@

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  12. Express sintheta+sin3theta and sin5theta+sin7theta in product form

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

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

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

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  16. Express sin3A and cos2A in terms of sine function

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

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

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

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

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