Hard - Trigonometric function

May 2010
64
0
Palmy
Help me solve this question. Can't seem to grasp the formula


4)Given that sin 55degrees = 0.819 and cos20degrees = 0.94,
show how you would use the identities for sin(A+B) and cos(A+B) to find the following:
a) sin 75degrees
b) cos 35 degrees
c) tan 35 degrees
Showing the steps you would follow. NOTE: sin^2theta+cos^2theta=1
 
Feb 2010
1,036
386
Dirty South
Help me solve this question. Can't seem to grasp the formula


4)Given that sin 55degrees = 0.819 and cos20degrees = 0.94,
show how you would use the identities for sin(A+B) and cos(A+B) to find the following:
a) sin 75degrees
b) cos 35 degrees
c) tan 35 degrees
Showing the steps you would follow. NOTE: sin^2theta+cos^2theta=1
sin(A+B) = sinAcosB+cosAsinB

so sin75=sin(55+20)=sin55.cos20+cos55.sin20

cos(A-B) = cosA.cosB+sinA.sinB

so cos35= cos(55-20)=cos55.cos20+sin55.sin20
 
May 2010
64
0
Palmy
Thanks

Thanks for your help again.....Just wondering how you find c) Tan


sin(A+B) = sinAcosB+cosAsinB

so sin75=sin(55+20)=sin55.cos20+cos55.sin20

cos(A-B) = cosA.cosB+sinA.sinB

so cos35= cos(55-20)=cos55.cos20+sin55.sin20
 
Feb 2010
1,036
386
Dirty South
Thanks for your help again.....Just wondering how you find c) Tan
\(\displaystyle tan(A-B)=\frac{sin(A-B)}{cos(A-B)}\)

or

\(\displaystyle tan(A-B) = \frac{tanA-tanB}{1+tanA.tanB}\)
 
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