Q. In a right triangle, cos(2x)∘=sin(7x−7)∘. Solve for x. Round your answer to the nearest hundredth if necessary.
Apply Pythagorean Identity: Since we have cos(2x)2 and sin(7x−7)2, we can use the Pythagorean identity sin2(θ)+cos2(θ)=1. This means that cos2(θ)=1−sin2(θ). So, we can replace cos(2x)2 with 1−sin2(2x).
Set Equation to Zero: Now we have 1−sin2(2x)=sin2(7x−7). Let's move everything to one side to set the equation to zero: sin2(2x)+sin2(7x−7)−1=0.
Use Sine Double Angle Identity: We can use the sine double angle identity sin(2θ)=2sin(θ)cos(θ). But we need to express sin2(2x) in terms of sin and cos. So, we'll use the identity sin2(θ)=21−cos(2θ).
Simplify Equation: Applying the identity to sin2(2x), we get (1−cos(4x))/2. Now our equation looks like (1−cos(4x))/2+sin2(7x−7)−1=0.
Combine Like Terms: Simplify the equation by multiplying everything by 2 to get rid of the fraction: 1−cos(4x)+2sin2(7x−7)−2=0.
Use Sine Double Angle Identity Again: Combine like terms: −cos(4x)+2sin2(7x−7)−1=0.
Substitute into Equation: We can use the identity sin2(θ)=21−cos(2θ) again for sin2(7x−7). This gives us 21−cos(14x−14).
Simplify Equation: Substitute this into our equation: −cos(4x)+2(21−cos(14x−14))−1=0.
Combine Like Terms: Simplify the equation: −cos(4x)+(1−cos(14x−14))−1=0.
Combine Like Terms: Simplify the equation: −cos(4x)+(1−cos(14x−14))−1=0. Combine like terms again: −cos(4x)−cos(14x−14)=0.
More problems from Find trigonometric functions using a calculator