Answer:

To evaluate the given expression, we can use the identities:

cos(45°) = 1/√2

sin(90°) = 1

Substituting these values into the expression, we get:

90°cos45°-sin90°sin45°

= 90°(1/√2) - 1(1/√2)

= -1/√2

Therefore, the given expression is equal to -1/√2.

Verified answer

Answer:

We know the values,

cos45°= 1/√2

sin90°= 1

sin45= 1/√2

Explanation:

Now if we put the values of cos90° which is 0 in the blank we get the result.

Putting cos in the blank,

cos90°cos45°-sin90°sin45°

=> 0 × 1/√2 - 1 × 1/√2

=> 0 -  1/√2

=>  -1/√2

Hence, the answer is cos90°.

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