SOLUTION: If sin a equal 2/3 and cos b equal 2/5 what is cos a+b

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Question 1026324: If sin a equal 2/3 and cos b equal 2/5 what is cos a+b
Answer by Cromlix(4381) About Me  (Show Source):
You can put this solution on YOUR website!
Hi there,
If sin a = 2/3
cos a = √5/3
If cos b = 2/5
sin b = √21/5
...........
cos(a + b) expands to:
cosacosb - sinasinb
√5/3 2/5 - 2/3 √21/5
2√5/15 - 2√21/15
2(√5 - √21)/15
Hope this helps :-)