Find all solutions of cos^4(2x)=9/16

15 degrees

Step-by-step explanation:

Given the trigonometry equation cos^4(2x)=9/16

cos^4(2x)=9/16

This an also be expressed as;

(cos²2x)² = 9/16

cos²2x = ±√9/16

cos²2x = ±3/4

cos2x = √3/4

cos2x = √3/2

2x = arccos √3/2

2x = 30

x = 30/2

x = 15degrees

Hence the value of x is 15 degrees

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18