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# C3 Domain and Range help. Watch

1. Thats the question, I get part A, however I do not understand how to do part B and C could someone help me please

2. (Original post by Jahmed228)

Thats the question, I get part A, however I do not understand how to do part B and C could someone help me please

First off you are restricted to x >/= 0 by the fact that this is the domain for g. Then f is only defined on 0 </= x </= pi, so fg is only defined when 0 </= g(x) = x +pi/2 </= pi This yields -pi/2 </= x </= pi/2 but since x >/= 0 we restrict this hence the answer

Note then that cos(x + pi/2) = -sinx, and on the domain you just found the range is easily deduced

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