Question

Solve the following equation for 0° ≤ θ < 360°. Use the "^" key on the keyboard to indicate an exponent. For example, sin2x would be typed as sin^2x. Be sure to show all your work.2sin2x - cos2x - 2 = 0

Answer 1

Answer: 2sin^2x+sin2x+cos2x=0 ..... (1).

By using the trigonometric identities below :

sin2x=2sinxcosx

cos2x=cos^2x-sin^2x

We substitute the trigonometric identities into (1).

2sin^2x+2sinxcosx+cos^2x-sin^2x=0

By combining like terms .

sin^2x+2sinxcosx+cos^2x=0.....(2)

The equation (2) is equivalent to the following expression (3).

(sinx+cosx)(sinx+cosx)=0 .....(3).

sinx+cosx=0

cosx=-sinx

divide both sides by cosx

1=-sinx/cosx

-1=sinx/cosx

sinx/cosx=tanx

substitute

-1=tanx

tanx=-1

tangent is negative in 2nd and 4th quadrants

tan135º=-1 (one answer)

tan315º=-1 (second answer)

Step-by-step explanation:

Please refer to the trigonometric identities used and explained above .