SINE AND COSINE AS COMPLEMENTS ~ adapted from Walch
Education
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Examine HEY! DOES THIS RELATIONSHIP WORK FOR sin B AND cos
A?
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In, sin A = cos B, and sin B = cos A This relationship between
sine and cosine is known as an identity Using this triangle, show
that this relationship works for every right triangle
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WHAT ELSE?!? The two acute angles in a right triangle have a
sum of 90. They are complementary angles. WWhat is the mathematical
expression?
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COFUNCTION IDENTITIES This looks like something I should
remember
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OHTHATS WHAT THAT MEANS The value of one ratio for one angle is
the same as the value of the other ratio for the other angle. So we
can use the sine of one acute angle to find the cosine of its
complementary angle (AND VICE VERSA)
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Lets try this example: Find
Slide 9
First step: Second step: Third step: Verify using a scientific
calculator. GREAT JOB
Slide 10
See if you can figure this one out. Be ready to explain which
identity you used and why: Find a value of for which sin = cos 15
is true.