Originally Posted by
shant112
can someone help me solve this problem please
1/1-sinx + 1/1+sinx=2sec^2x
I like this problem!
1/(1-sinx) + 1/(1+sinx) = 2sec^2(x) can be rewritten as:
1/(1-sinx) + 1/(1+sinx) = 2/cos^2(x) since 1/cos = sec
Now, multiply the whole equation by (1-sinx)(1+sinx)
Significant cross-cancelling will give you:
(1+sinx) + (1-sinx) = 2(1-sinx)(1+sinx)/cos^2(x)
Notice that the sinx and -sinx cancel out, leaving you:
1 + 1 = 2(1-sinx)(1+sinx)/cos^2(x)
Now, if you FOIL out the binomials, you get 2(1-sin^2x)/cos^2x
(1-sin^2x) actually equals cos^2x so you end up with:
2 cos^2x /cos^2x which just equals 2.
So, when all is said and done, you have 1+1 = 2 which is always true.
Now, you have a couple of times when x CANNOT equal something. For instance, x cannot equal 90 degrees (pi/2 radians) because sinx would equal -1, causing 1/0 in our original equation. Same with x = 270 (3pi/2 radians).
So, your solution is all reals except 90 and 270.