Find R, ? so 4sintheta + 3costheta = Rsin(?+ theta)

adambinch

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Mar 8, 2008
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Can anyone please help with following

i) Find R and ? such that

4sintheta + 3costheta = Rsin( ?+ theta) ,

where 0degrees is less than or equal to ? which is less than or equal to 360degrees

I've equated the coefficients Rcos?=4 Rsin?=3
Squared them and added them together giving R and then solved for ?

R2cos2? + R2sin2? = 42 + 32
R2(cos2? + sin2?) = 25
R = 5

ii) Finding all the solutions to the equation

tanx = 1.6

where -360degrees is less than or equal to x which is less than or equal to 360degrees
 
adambinch said:
Can anyone please help with following

i) Find R and ? such that

4sintheta + 3costheta = Rsin( ?+ theta) ,

where 0degrees is less than or equal to ? which is less than or equal to 360degrees

I've equated the coefficients Rcos?=4 Rsin?=3
Squared them and added them together giving R and then solved for ?

R2cos2? + R2sin2? = 42 + 32
R2(cos2? + sin2?) = 25
R = 5

Are you allowed to use a calculator?

ii) Finding all the solutions to the equation

tanx = 1.6

where -360degrees is less than or equal to x which is less than or equal to 360degrees
 
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