Four teaching plans for compulsory mathematics in People's Education Press. - Training Enrollment Network

Four teaching plans for compulsory mathematics in People's Education Press.

1, it is known that tan a=-3/4, and a is in quadrant 2 and quadrant 4.

(1)a is in quadrant 2. SIN 2A+COS 2A = 1 Sina/COSA =-3/4 Sina > 0 COSA & lt； 0

Sina=3/5 cosa=-4/5。

(2)a is in quadrant 4. SIN 2A+COS 2A = 1 Sina/COSA =-3/4 Sina

Sina=-3/5 cosa=4/5。

2. Given sin x=- 1/3, find the values of cos x and tan x..

X is in quadrant 3 and quadrant 4.

(1)x is in the three-quadrant cosx.

sin^2x+cos^2x= 1 cosx =-2√2/3 tanx = sinx/cosa =√2/4

(2)x is in 4 quadrant cosx >; 0

sin^2x+cos^2x= 1 cosx = 2√2/3 tanx = sinx/cosa =-√2/4

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