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sn - 6 and sin - 10. find the values710, find the valuesof cos A and cos B. Hence using the formulacos (A + B) = cos A cos B-sin A sin B, show thatBoard Term-1, 2012, Set-55]A+B=45°. |
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Answer» SinA =1/√5cosA=√(1-sin²A) (sin²A+cos²A=1)=√1-1/√5² (1-cos²A=sin²A=√1-1/5. (cosA=√1-sin²A) =√5-1/5=√4/5cosA=2/√5sinB =1/√10cosB=√1-sin²B=√1-1/√10²=√1-1/10=√10-1/10=√9/10cosB=3/√10Cos(A+B)=cosA. cosB-sinA. sinB=2/√5 x 3/√10 - 1/√5 x 1/√10=6/√50-1/√50=5/√50=5/5√2=1/√2cos(A+B)=1/√2Cos(A+B)=Cos 45°A+B=45° |
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