Q. If cosθ=61, then what is the positive value of tan21θ, in simplest radical form with a rational denominator?
Apply double angle formula: Use the double angle formula for tangent: tan(21θ)=±1+cos(θ)1−cos(θ). Substitute cos(θ)=61 into the formula. tan(21θ)=±1+611−61.
Substitute cos(θ): Simplify the expression inside the square root.tan(21θ)=±(66−61)/(66+61).tan(21θ)=±(65)/(67).
Simplify expression: Simplify the fraction inside the square root by multiplying the numerator and denominator by 6.tan(21θ)=±75.
Simplify fraction: Since we are looking for the positive value, choose the positive square root. tan(21θ)=75.
Choose positive value: Rationalize the denominator.tan(21θ)=75×77.tan(21θ)=4935.
Rationalize denominator: Simplify the square root. tan(21θ)=735.
More problems from Find trigonometric ratios using multiple identities