Equation involving trigonometric function defined above are call trigonemtric
equation. Since we know that value of sin and cos function repeat after 2π
interval and value of tan function repeat after π interval.So there will be
infinite solution for these equations.We define two forms of solutions here
The solution in the rangle 0 ≤ x ≤ 2π
The expression involving integer n which gives all solutions
of a trigonometric equation is called the general solution.
We shall use 'Z' to denote the set of integers.
Some Important points in that regard
sin x = 0 implies x = nπ, where n is any integer
cos x = 0 implies x = (2n + 1)(π/2)
sinx =siny then x=nπ+(-1)n
y where n is any integer
cosx=cosy then x=2nπ+y or x=2nπ- y where n is any integer
tanx=tany then x=nπ+y or x=nπ- y where n is any integer
Some basics Tips to solve the trigonometry questions
1) Always try to bring the multiple angles to single angles using basic formla.Make sure all your angles are the same. Using sin(2X) and
sinX is difficult, but if you use sin2X = 2sin(x)cos(x), that leaves sin(x) and cos(x),
and now all your functions match.
The same goes for addition and subtraction: don't try
working with sin(X+Y) and sinX. Instead, use sin(X+Y) = sin(x)cos(y)+cos(x)sin(y) so that all
the angles match
2) Converting to sin and cos all the items in the problem using basic formula. I have mentioned sin and cos as they are easy to solve.You can use any other also.
3) Check all the angles for sums and differences and use the appropriate identities to remove them.
4) Use phythagorean identifies to simplfy the equations
5) Practice and Practice. You will soon start figuring out the equation and there symmetry to resolve them fast
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