Need some urgent help solving double argument properties for Calc/Trig course. Anybody out there that can help?

If cos A=3/5 and 0<A<90, find sin 2A and cos 1/2 A

Any help on this?

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- Dec 20th 2006, 05:36 PMSevens[SOLVED] double argument properties
Need some urgent help solving double argument properties for Calc/Trig course. Anybody out there that can help?

If cos A=3/5 and 0<A<90, find sin 2A and cos 1/2 A

Any help on this? - Dec 20th 2006, 09:32 PMSoroban
Hello, Sevens!

You're expected to know the necessary identities:

. .

. .

Quote:

If and , find and

[1] Since , we have a 3-4-5 right triangle. . Hence: .

Therefore: .

[2]