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anonymous
 4 years ago
if a and b are two angles in Quadrant II such that tan a = 1/2 and tan B = 2/3 find cos(a+b)
anonymous
 4 years ago
if a and b are two angles in Quadrant II such that tan a = 1/2 and tan B = 2/3 find cos(a+b)

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anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0You can use the mother equation to derive cos(a+b)=cos(a)cos(b)sin(a)sin(b) dw:1327888004419:dw 3/2sin(b) = cos(b) 2sin(a) = cos(a) cos(a+b) = 3sin(a)sin(b)1/3cos(a)cos(b) take your pick = 3/2cos(a)(2/3cos(b))1/3cos(a)cos(b) = 2/3cos(a)cos(b)

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0Thank you for your help on that, is there anyway you could help me with some more math problems? such as 35. Verify that cos(90+A) =sin A is an identity?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0just plug and chug cos(90+A)=cos(90)cos(A)sin(90)sin(A) cos(90)=0, since d/dx sin(x)=cos(x) and sin(90)=1, so you have 1*sin(A) = sin(A)
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