SOLUTION: Let cosA=-5/13 with A in Q3 and sinB=3/5 with B in Q1. Find sin(A-B), cos(A-B), and tan(A-B). All I know how so far is just the formula sin(A-B)=sinAcosB-cosAsinB and cos(A-B)=c

Algebra ->  Trigonometry-basics -> SOLUTION: Let cosA=-5/13 with A in Q3 and sinB=3/5 with B in Q1. Find sin(A-B), cos(A-B), and tan(A-B). All I know how so far is just the formula sin(A-B)=sinAcosB-cosAsinB and cos(A-B)=c      Log On


   

Question 1162379: Let cosA=-5/13 with A in Q3 and sinB=3/5 with B in Q1. Find sin(A-B), cos(A-B), and tan(A-B).
All I know how so far is just the formula sin(A-B)=sinAcosB-cosAsinB and cos(A-B)=cosAcosB+sinAsinB.
Found 2 solutions by greenestamps, ikleyn:
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


5-12-13 and 3-4-5 are Pythagorean Triples.

Given cosA = -5/12, sinA is 12/13 or -12/13, depending on the quadrant.

Given sinB = 3/5, cosB is 4/5 or -4/5, depending on the quadrant.

After you find sinA and cosB, use the formulas you show to find sin(A-B) and cos(A-B).

Then tan(A-B) is just sin(A-B) divided by cos(A-B).

Answer by ikleyn(52797) About Me  (Show Source):
You can put this solution on YOUR website!
.

For many similar solved problems  (your  TEMPLATES)  see the lessons
    - Calculating trigonometric functions of angles
    - Advanced problems on calculating trigonometric functions of angles
    - Evaluating trigonometric expressions
in this site.

Learn from there as much as you can (!) (!)

Also,  you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic  "Trigonometry: Solved problems".


Save the link to this textbook together with its description

Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson

into your archive and use when it is needed.