Rewrite the equation as .

Multiply by .

Add to both sides of the equation.

Divide each term in by .

Cancel the common factor of .

Cancel the common factor.

Divide by .

Cancel the common factor of and .

Factor out of .

Cancel the common factors.

Factor out of .

Cancel the common factor.

Rewrite the expression.

Subtract from both sides of the equation.

Simplify the left side of the equation.

To write as a fraction with a common denominator, multiply by .

Write each expression with a common denominator of , by multiplying each by an appropriate factor of .

Combine.

Multiply by .

Combine the numerators over the common denominator.

Move to the left of .

Multiply both sides of the equation by .

Remove parentheses.

Factor out of .

Cancel the common factor.

Rewrite the expression.

Add to both sides of the equation.

Divide each term in by .

Cancel the common factor of .

Cancel the common factor.

Divide by .

Multiply .

Multiply and .

Multiply by .

Rewrite the equation as .

Subtract from both sides of the equation.

Multiply both sides of the equation by .

Simplify the left side.

Cancel the common factor of .

Cancel the common factor.

Rewrite the expression.

Cancel the common factor of .

Factor out of .

Cancel the common factor.

Rewrite the expression.

Simplify .

Apply the distributive property.

Combine and .

Cancel the common factor of .

Move the leading negative in into the numerator.

Factor out of .

Cancel the common factor.

Rewrite the expression.

Multiply and .

Simplify the expression.

Multiply by .

Move the negative in front of the fraction.

Solve for a k=420*cos(a+b)-455*cos(a)