mathpretrighelp
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- Dec 11, 2005
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find the exact value of the expressions cos (alpha +beta), sin (alpha+beta),tan (alpha+beta)
given cos (alpha)=24/25, alpha lies in quadrant 4 and sin (beta)= -3/7, beta lies in quadrant 3
what i am having trouble in is mainly the algebra part of it. i understand the concepts in getting the answers, but when i start dealing with radicals i get really confuse.
this is what i know by solving the above problems( i dont know if i solve the bolded ones correctly, but this may be the reason why my answers the problems look funny. the ones in bold are the ones i solved)
cos (alpha)=24/25
sin (alpha) = -7/25
sin (beta) = -3/7
cos (beta) = -2 sqrt 10/7
solving for cos (alpha +beta). i used the formula
cos (alpha +beta)= cos alpha cos beta-sin alpha sin beta
pluging in the values from above
i got
-(48 sqrt 10 + 21)/175
solving for sin (alpha+beta) i used sin
(alpha+beta)=sin alpha cos beta + cos alpha sin beta
i got
(2 sqrt 10 - 72)/25
solving for
tan (alpha+beta)=(tan alpha+ tan beta)/(1- tan alpha tan beta)
i got (-140+72 sqrt 10)/(480 -21 sqrt 10)
i know this answer is totally wrong.
any help is muchly appreciated
thanks in advance!
given cos (alpha)=24/25, alpha lies in quadrant 4 and sin (beta)= -3/7, beta lies in quadrant 3
what i am having trouble in is mainly the algebra part of it. i understand the concepts in getting the answers, but when i start dealing with radicals i get really confuse.
this is what i know by solving the above problems( i dont know if i solve the bolded ones correctly, but this may be the reason why my answers the problems look funny. the ones in bold are the ones i solved)
cos (alpha)=24/25
sin (alpha) = -7/25
sin (beta) = -3/7
cos (beta) = -2 sqrt 10/7
solving for cos (alpha +beta). i used the formula
cos (alpha +beta)= cos alpha cos beta-sin alpha sin beta
pluging in the values from above
i got
-(48 sqrt 10 + 21)/175
solving for sin (alpha+beta) i used sin
(alpha+beta)=sin alpha cos beta + cos alpha sin beta
i got
(2 sqrt 10 - 72)/25
solving for
tan (alpha+beta)=(tan alpha+ tan beta)/(1- tan alpha tan beta)
i got (-140+72 sqrt 10)/(480 -21 sqrt 10)
i know this answer is totally wrong.
any help is muchly appreciated
thanks in advance!