Im asking how to go about solving questions like these..I know how to get alpha and beta just have only done (a+b), (a), or (b).
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Just as with cos(a+b), you have:
(1) (cos(2a) * cos(b)) - (sin(2a) * sin(b) <---- First critical step
Since: (2) cos(2a) = cos^2(a) - sin^2(a) and (3) sin(2a) = 2*sin(a)*sin(b) the answer is
([cos^2(a) - sin^2(a)] * cos(b)) - ([2sin(a)*sin(b)] * sin(b)) <----- Final Answer
where I have merely substituted (2) and (3) into (1) and hopefully kept balanced
parentheses.
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tan(b/2) = csc(b) - cot(b) (This is a basic trigonometric identity.)
See Wikipedia if you don't trust my memory. I won't be offended. It's probably
under something like "half angle formulas".
.
(1) (cos(2a) * cos(b)) - (sin(2a) * sin(b) <---- First critical step
Since: (2) cos(2a) = cos^2(a) - sin^2(a) and (3) sin(2a) = 2*sin(a)*sin(b) the answer is
([cos^2(a) - sin^2(a)] * cos(b)) - ([2sin(a)*sin(b)] * sin(b)) <----- Final Answer
where I have merely substituted (2) and (3) into (1) and hopefully kept balanced
parentheses.
----------
tan(b/2) = csc(b) - cot(b) (This is a basic trigonometric identity.)
See Wikipedia if you don't trust my memory. I won't be offended. It's probably
under something like "half angle formulas".
.