$sin (2 \alpha) =2\cdot sin \alpha \cdot cos \alpha \\cos(2 \alpha )=1-2sin^2 \alpha \\-------------------- \\cos2x-sin2x=1-2sin2x\\cos2x+sin2x=1\\1-2sin^2x+2sinx\cdot cosx=1\\-2sinx(sin x-cosx)=0\\ -2sinx=0\ \ \ \ or\ \ \ \ sinx-cosx=0\\\\1)\ -2sinx=0\ \ \Leftrightarrow\ \ sinx=0\ \ \Leftrightarrow\ \ x_1=k \pi \ \ and\ \ k\in I\\2)\ \ sinx-cosx=0\ \ \Leftrightarrow\ \ sinx=cosx\ /:cosx\ \ \ \ \ \wedge\ \ \ \ cos x \neq 0\\tanx=1\ \ \Leftrightarrow\ \ x_2= \frac{ \pi }{4} +k \pi \ \ and\ \ k\in I$

3 0

3 years ago

How can u tell <br> Whether 1080 is cube number

dolphi86 [110]

TSplit into prime factors

1080 = 2*2*2*3*3*3*5

Its not a cube because although there are 2 triplicates there is also a 5.

Note 2*2*2*3*3*3 is a cube.

3 0

3 years ago

Read 2 more answers

The graphs of the equations 4x - y = 6 and x + y = 4 intersect at

Mars2501 [29]

Solve by Substitution
D. X=2 Y=2.

5 0

3 years ago