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Lösung 4.3:7b

Aus Online Mathematik Brückenkurs 1

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Version vom 15:08, 22. Okt. 2008

Using the addition formula, we rewrite sin(x+y) as

sin(x+y)=sinxcosy+cosxsiny.

If we use the same solution procedure as in exercise a, we use the Pythagorean identity cos2v+sin2v=1 to express the unknown factors sinx and siny in terms of cosx and cosy,

sinxsiny=1cos2x=1522=1425=521=1cos2y=1532=1925=54.

The angles x and y lie in the first quadrant and both sinx and siny are therefore positive, i.e.

sinx=521andsiny=54. 

Thus, the answer is

sin(x+y)=52153+5254=25321+8.