:< вычислите 1 )sin^2a, если tga=2 2) tg(pi/4-2x), если tgx=2

sina/cosa=2

sina=2cosa

sin^2a=4cos^2a

sin^2a+4sin^2a=4

sin^2a=4/5

2)

tg(pi/4-2x)=(tg45-tg2x)/(1+tg2xtg45)=(1-tg2x)/(1+tg2x)

tg2x=2tgx/(1-tgx^2)=4/(1-4)=-4/3

tg(pi/4-2x)=(1+4/3)/(1-4/3)=(7/3)/(-1/3)=-7

-12, -15, -18, -21, -24

1)

(1/2+a)^2=1/4+a+a^2

2)

(m+0,2)^2=m^2+0,4m+0,04

3)

(x+1/3)^2=x^2+2x/3+1/9

4)

(1,1+p)^2=1,21+2,2p+p^2

5)

(1/2a+2/3b)^2=a^2/4+2ab/3+4b^2/9

6)

(3/4x+1,5y)^2=9x^2/16+2,25xy+2,25y^2

7)

(0,2m+2,1n)^2=0,04m^2+0,84mn+4,41n^2

8)

(0,4p+0,3q)^2=0,16p^2+0,24mn+0,09q^2

9)

(3/5ab+1/2c)^2=9a^2b^2/25+0,6abc+c^2/4