Posted by **saad** on Monday, August 15, 2011 at 12:32am.

Solve the equation for cos theta-tan theta=0 for greater than or egual to zero but less than 2pi. Write your answer as a multiple of pi, if possible form the following choices:

pi , 5pi

A. --- ----

4___ 4

B. pi 3pi 5pi 7pi

----- '----- '-----'-----

4_____ 4_____ 4______4

C. pi 3pi 3pi 7pi

----- '----- '-----'-----

2_______4______2_____4

D. pi 7pi 3pi 11pi

----- '----- '-----'-----

2________6______2_____6

- trig -
**Anonymous**, Monday, August 15, 2011 at 2:08am
cos ( theta ) - tan ( theta) = 0

tan ( theta ) = sin (theta ) / cos( theta )

cos ( theta ) - tan ( theta ) =0

cos ( theta ) = tan ( theta )

cos ( theta ) = sin ( theta ) / cos ( theta )

cos^2 ( theta) = sin ( theta )

Now go on:

wolframalpha dot com

When page be open in rectangle type :

solve cos^2 ( theta) = sin ( theta )

and click =

After few seconds you will see solution.

Then click option Show steps

- trig -
**Reiny**, Monday, August 15, 2011 at 8:48am
cosŲ - tanŲ = 0

cosŲ - sinŲ/cosŲ = 0

multiply by cosŲ

cos^2Ų - sinŲ = 0

(1 - sin^2Ų) - sinŲ = 0

sin^2Ų + sinŲ - 1 = 0

sinŲ = (-1 ± √5)/2

sinŲ = .618034 or -1.608 , the last is not possible since sinŲ has to be between -1 and +1

Ų = 38.17° from my calculator (or 141.83°)

All your choices are in radians in multiples of π/2, π/4 or π/6

which would be multiples of 90°, 45° or 30°

None of these match,

btw, my answers satisfies the original equation.

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