Question

3(1-tan y cos y)=5 cos²y - 2 for 0°<y<360°​

Answer 1

Answer:

z=x+y

cos

2

x+cos

2

y+cos

2

z−2cosx.cosy.cosz

=cos

2

x+cos

2

y+cos

2

(x+y)−2cosx.cosy.cos(x+y)

=cos

2

x+cos

2

y+(cosxcosy−sinxsiny)

2

−2cosxcosy[cosxcosy−sinxsiny]

=cos

2

x+cos

2

y+cos

2

xcos

2

y+sin

2

xsin

2

y−2cosxcosysinxsiny−2cos

2

xcos

2

y+2cosxcosysinxsiny

=cos

2

x+cos

2

y−cos

2

xcos

2

y+sin

2

xsin

2

y

=cos

2

x+cos

2

y−cos

2

xcos

2

y+sin

2

x(1−cos

2

y)

=cos

2

x+cos

2

y−cos

2

xcos

2

y+sin

2

x−sin

2

xcos

2

y

=cos

2

x+sin

2

x+cos

2

y−cos

2

y(cos

2

x+sin

2

x)

=1