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Prove that: cos 2theta"cos"(theta)/(2...

Prove that:
`cos 2theta"cos"(theta)/(2)-cos 3theta cos((9theta)/2)="sin" 5theta "sin"((5theta)/2)`.

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MODERN PUBLICATION-TRIGONOMETRY-FREQUENTLY ASKED QUESTIONS
  1. Find the maximum and minimum values of 7costheta + 24sintheta

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  2. Prove that 5costheta+3cos(theta+pi/3)+3 lies between -4a n d10.

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  3. Prove that: cos 2theta"cos"(theta)/(2)-cos 3theta cos((9theta)/2)="...

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  4. Prove that (2cos2A+1)/(2cos2A-1)=tan(60^0+A)tan(60^0-A)dot

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  5. " sin " (150^(@) + x) + " sin " (150^(@) -x) " = cos x"

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  6. If the angles A,B,C are in A.P., prove that cot B=("sin" A-"sin" C)/(c...

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  7. (cosalpha+cosbeta)^2+(sinalpha-sinbeta)^2=4cos^2(alpha+beta)/2

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  8. If "sin" theta+"sin" phi=sqrt3(cos phi-cos theta),prove that: "sin"...

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  9. prove that ((cosA+cosB)/(sinA-sinB))^n+((sinA+sinB)/(cosA-cosB))^n=2co...

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  10. If sin x+"sin" y=a and cos x+cos y=b, find the values of: (i) "tan...

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  11. Prove that sin 10^(@) " sin " 50^(@) " sin " 60^(@) " sin " 70^(@) ...

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  12. (sin 5x + sin 3x)/(cos 5x + cos 3x) = tan 4x

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  13. Prove that n( " cos " 4x + " cos " 3x + " cos " 2x)/(" sin " 4x +...

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  14. (( sin 7x + sin 5x)+(sin 9x + sin 3x))/((cos 7x + cos 5x)+(cos 9x+ cos...

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  15. Prove that cosalpha+cosbeta+cosgamma+cos(alpha+beta+gamma)=4cos((alpha...

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  16. If s intheta=n"sin"(theta+2alpha) , prove that tan(theta+alpha)=(1+n)/...

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  17. If alpha+beta+90^0 , find the maximum and minimum values of s inalphas...

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  18. Prove that (tan 5theta + tan 3theta)/(tan 5theta - tan 3theta) = 4 c...

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  19. Find "sin" 2theta when "sin" theta+cos theta=1.

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  20. Prove that: "tan"A+cotA=2"cosec" 2A and deduce that "tan" 75^(@)+co...

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