Is (1+tan^2(θ))cos^2(θ)=1 ?

The answer to whether (1+tan^2(θ))cos^2(θ)=1 is True

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prove (1+tan^2(θ))cos^2(θ)=1

prove

(1 + tan^{2} (θ)) cos^{2} (θ) = 1

True

Solution steps

(1 + tan^{2} (θ)) cos^{2} (θ) = 1

Manipulating left side

(1 + tan^{2} (θ)) cos^{2} (θ)

Express with sin, cos

(1 + tan^{2} (θ)) cos^{2} (θ)

Use the basic trigonometric identity:

tan (x) = \frac{sin ( x )}{cos ( x )}

= (1 + (\frac{sin ( θ )}{cos ( θ )})^{2}) cos^{2} (θ)

Simplify

(1 + (\frac{sin ( θ )}{cos ( θ )})^{2}) cos^{2} (θ) : cos^{2} (θ) + sin^{2} (θ)

(1 + (\frac{sin ( θ )}{cos ( θ )})^{2}) cos^{2} (θ)

Apply exponent rule:

(\frac{a}{b})^{c} = \frac{a ^{c}}{b ^{c}}

= cos^{2} (θ) (\frac{sin ^{2} ( θ )}{cos ^{2} ( θ )} + 1)

Join

1 + \frac{sin ^{2} ( θ )}{cos ^{2} ( θ )} : \frac{cos ^{2} ( θ ) + sin ^{2} ( θ )}{cos ^{2} ( θ )}

1 + \frac{sin ^{2} ( θ )}{cos ^{2} ( θ )}

Convert element to fraction:

1 = \frac{1 cos ^{2} ( θ )}{cos ^{2} ( θ )}

= \frac{1 \cdot cos ^{2} ( θ )}{cos ^{2} ( θ )} + \frac{sin ^{2} ( θ )}{cos ^{2} ( θ )}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{1 \cdot cos ^{2} ( θ ) + sin ^{2} ( θ )}{cos ^{2} ( θ )}

Multiply:

1 \cdot cos^{2} (θ) = cos^{2} (θ)

= \frac{cos ^{2} ( θ ) + sin ^{2} ( θ )}{cos ^{2} ( θ )}

= \frac{cos ^{2} ( θ ) + sin ^{2} ( θ )}{cos ^{2} ( θ )} cos^{2} (θ)

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{( cos ^{2} ( θ ) + sin ^{2} ( θ ) ) cos ^{2} ( θ )}{cos ^{2} ( θ )}

Cancel the common factor:

cos^{2} (θ)

= cos^{2} (θ) + sin^{2} (θ)

= cos^{2} (θ) + sin^{2} (θ)

= cos^{2} (θ) + sin^{2} (θ)

Rewrite using trig identities

cos^{2} (θ) + sin^{2} (θ)

Use the Pythagorean identity:

cos^{2} (x) + sin^{2} (x) = 1

= 1

= 1

We showed that the two sides could take the same form

\Rightarrow True

cos (x - y) + cos (x + y) = 2 cos (x) cos (y)

sin (\frac{π}{6} + x) + sin (\frac{π}{6} - x) = cos (x)

\frac{tan ^{2} ( x )}{tan ^{2} ( x ) + 1} = sin^{2} (x)

(csc (x) + 1) (csc (x) - 1) = cot^{2} (x)

(cot (x) - csc (x)) (cos (x) + 1) = - sin (x)

Is (1+tan^2(θ))cos^2(θ)=1 ?
The answer to whether (1+tan^2(θ))cos^2(θ)=1 is True