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Show that cos^4""pi/8+cos^4""(3pi)/8+cos...

Show that `cos^4""pi/8+cos^4""(3pi)/8+cos^4""(5pi)/8+cos^4""(7pi)/8=3/2`

A

`1/2`

B

`3/2`

C

`3/4`

D

`1/4`

Text Solution

Verified by Experts

The correct Answer is:
B
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AAKASH SERIES-MULTIPLE & SUBMULTIPLE ANGLES-EXERCISE-II
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  3. Show that cos^4""pi/8+cos^4""(3pi)/8+cos^4""(5pi)/8+cos^4""(7pi)/8=3/2

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  8. cos^(2)(alpha+beta)+cos^(2)(alpha-beta)-cos2alpha cos2beta=

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  9. If cos^(3) theta + cos^(3)((2pi)/(3) + theta) + cos^(3)((4pi)/(3) + th...

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  10. If tan(theta/2)=cosec theta-sintheta then the numerical balue of "cos"...

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  11. If cos theta = (cos alpha - cos beta)/(1-cos alpha cos beta), then one...

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  12. If x+y+z=xyz , " then " sum(3x-x^(3))/(1-3x^(2))=

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  14. If sin18^(@)=(sqrt5-1)/4 then Sin81^(@)=

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  15. If sqrt(1+sinA)-sqrt(1-sinA)=2"sin"A/2"then"A/2 in

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  16. If (3pi)/4ltA/2lt(5pi)/4 then -sqrt(1+sinA)+sqrt(1-sinA)=

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  17. I : If (cos alpha )/(a)=(sin alpha )/(b) then a cos 2 alpha + b cos 2...

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  18. If A=6 sin20^(@) - 8 sin^(3) 20^@ , B= 8 cos^(3) 20^(@)-6 cos 20^(@) ...

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  19. Match the following .{:((1) tan(pi/4+theta)-tan(pi/4-theta)=,(a) 1),...

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  20. Assertion (A): sqrt(4sin^(4)theta+sin^(2)2theta)+4cos^(2)(pi/4-theta/2...

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