Is cos(θ)=sec(θ)-(sin(θ))(tan(θ)) ?

The answer to whether cos(θ)=sec(θ)-(sin(θ))(tan(θ)) is True

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

prove cos(θ)=sec(θ)-(sin(θ))(tan(θ))

prove

cos (θ) = sec (θ) - (sin (θ)) (tan (θ))

True

Solution steps

cos (θ) = sec (θ) - sin (θ) tan (θ)

Manipulating right side

sec (θ) - sin (θ) tan (θ)

Express with sin, cos

sec (θ) - sin (θ) tan (θ)

Use the basic trigonometric identity:

sec (x) = \frac{1}{cos ( x )}

= \frac{1}{cos ( θ )} - sin (θ) tan (θ)

Use the basic trigonometric identity:

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

= \frac{1}{cos ( θ )} - sin (θ) \frac{sin ( θ )}{cos ( θ )}

Simplify

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

\frac{1}{cos ( θ )} - sin (θ) \frac{sin ( θ )}{cos ( θ )}

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

sin (θ) \frac{sin ( θ )}{cos ( θ )}

Multiply fractions:

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

= \frac{sin ( θ ) sin ( θ )}{cos ( θ )}

sin (θ) sin (θ) = sin^{2} (θ)

sin (θ) sin (θ)

Apply exponent rule:

a^{b} \cdot a^{c} = a^{b + c}

sin (θ) sin (θ) = sin^{1 + 1} (θ)

= sin^{1 + 1} (θ)

Add the numbers:

1 + 1 = 2

= sin^{2} (θ)

= \frac{sin ^{2} ( θ )}{cos ( θ )}

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

Apply rule

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

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

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

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

Rewrite using trig identities

\frac{1 - sin ^{2} ( θ )}{cos ( θ )}

Use the Pythagorean identity:

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

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

= \frac{cos ^{2} ( θ )}{cos ( θ )}

Cancel the common factor:

cos (θ)

= cos (θ)

= cos (θ)

We showed that the two sides could take the same form

\Rightarrow True

cos (2 x - 90) = 2 sin (x) cos (x)

sin^{4} (x) - 2 sin^{2} (x) = cos^{4} (x) - 1

cot^{4} (a) = \frac{cos ^{4} ( a )}{sin ^{4} ( a )}

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

3 sin (x) = cos (x)

Is cos(θ)=sec(θ)-(sin(θ))(tan(θ)) ?
The answer to whether cos(θ)=sec(θ)-(sin(θ))(tan(θ)) is True