cosx + sinx = 0 when sinx = -cosx.
By dividing both sides by cosx you get:
sinx/cosx = -1
tanx = -1
The values where tanx = -1 are 3pi/4, 7pi/4, etc.
Those are equivalent to 135 degrees, 315 degrees, etc.
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you need to explain it better but with what i got i if sin x equals b obviously sin 2x is double of b hence sin 2x is more than b. {Not obvious at all, actually. And the above is false. Sin(Pi/2) = 1 and Sin(Pi)=0. But clearly 2 is not greater than 0. Contradiction.} Obtuse means Pi/2 < x < Pi So, sin(x) = b means b>0, because sin(y) > 0 if 0<y<Pi sin(2x)=2sin(x)cos(x) cos(x) < 0 because cos(Pi/2)= 0 and the derivative is negative there. Hence, sin(2x) = 2 sin(x) cos(x) = 2*b*(-K), where K is a positive constant Since b>0, -2Kb < b
For the product to be zero, any of the factors must be zero, so you solve, separately, the two equations: sin x = 0 and: cos x = 0 Like many trigonometric equations, this will have an infinity of solutions, since sine and cosine are periodic functions.
lim(x->0) of sin(x)^2/x we use L'Hospital's Rule and derive the top and the bottomd/dx(sin(x)^2/x)=2*sin(x)*cos(x)/1lim(x->0) of 2*sin(x)*cos(x)=2*0*1=0
sin(x) = cos(x)sin(x)/cos(x) = tan(x) = 1x = arctan(1) = 45 degreessin(45)=cos(45) = Sqrt(2)/2 Answer: By observation. Since Sine = Opposite over hypotenuse and Cosine = Adjacent over hypotenuse. Any right angle triangle where the opposite and adjacent sides are the same length will have Sine equal to Cosine. This only happens with an isosceles triangle (two sides are equal in length). When one angle is 90o the other two are 45o.
It is minus 1 I did this: sinx/cos x = tan x sinx x = cosx tanx you have (x - sinxcosx) / (tanx -x) (x- cos^2 x tan x)/(tanx -x) let x =0 -cos^2 x (tanx) /tanx = -cos^x -cos^2 (0) = -1