SOLUTION: sen(a)= 3/5, &#960;/2 < a < &#960; and cos (B)=20/29, 0 < B <&#960;/2, sin (a-B)= ????

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Question 1031121: sen(a)= 3/5, π/2 < a < π and cos (B)=20/29, 0 < B <π/2, sin (a-B)= ????
Answer by ikleyn(52794) About Me  (Show Source):
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sen(a)= 3/5, π/2 < a < π and cos (B)=20/29, 0 < B <π/2, sin (a-B)= ????
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Use the formula  sin(a - b) = sin(a)*cos(b) - cos(a)*sin(b).
   (Regarding this formula, see the lesson Addition and subtraction formulas in this site.)


You need to know cos(a) and sin(b) in addition to the given sin(a) and cos(b).


Calculate

cos(a) = +/- sqrt%281-sin%5E2%28a%29%29. Choose correct sign before  sqrt  based on info about angle "a".

sin(b) = +/- sqrt%281-cos%5E2%28b%29%29. Choose correct sign before  sqrt  based on info about angle "b".

See the sample in the lesson Calculating trigonometric functions of angles>,  Problem 3.

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I was not able to read your original formula, and therefore corrected it by inserting the blank dividers.