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Trigonometry

Question no 61 and 62 both questions of top math I will be greatly for your help plz ............................................... ...... .....,

Question image for Question no 61 and 62 both questions of top math
Profile image of Ashiah Kumar
7 Years agoGrade
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2 Answers

Profile image of Susmita
7 Years ago
I am writing P in place of theta.
acosP-bsinP=c
Take whole square.
a2cos2P+b2sin2P-2abcosPsinP=c2
or,a2cos2P+b2sin2P=c2+2absocPsinP......eq1
Now (asinP+bcosP)2
=a2sin2P+b2cos2P+2absinPcosP
=a2(1-cos2P)+b2(1-sin2P)+2absinPcosP
=a2+b2-(a2cos2P+b2sin2P)+2absinPcosP
=a2+b2-(c2+2absinPcosP)+2absinPcosP
=a2+b2-c2
so asinP+bcosP=root(a2+b2-c2) with a plus minus sign before it
Profile image of Susmita
7 Years ago
sinx+sin2x=1
Or,1-sin2x=sinx
or,cos2x=sinx....eq1
cos8x+2cos6x+cos4x
=sin4x+2sin3x+sin2x
=sin2x(sin2x+2sinx+1).....eq2.
Replace sin2x=1-sinx and factorize the term within first bracket.eq2 will become
(1-sinx)(1+sinx)(1+sinx)
=(1-sin2x)(1+sinx) 
=sinx(1+sinx)
=sinx+sin2x=1
none of the given options are correct.
 
 

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