Posted by rick on Tuesday, February 26, 2008 at 1:24pm.
If sin = 4/5 with A in QII, and sin B = 3/5 with B in QIV find cos(AB)

trig  ^Quen^, Tuesday, February 26, 2008 at 8:46pm
cos(AB)= cosAcosB+sinAsinB
If sinA = 4/5 in QII
draw you triangle in QII, and find the third side.
The third side is 3. (Do the same thing for sin B= 3/5
Plug in:
cosAcosBsinAsinB
=(3/5)*(4/5)+(4/5)*(3/5)
=(12/25) (12/25)
=24/25

trig  Anonymous, Tuesday, September 11, 2012 at 7:59pm
53. the longest side is 55 cm. find the length of the shortest side
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