what is the exact value of sin (112.5*) using the half angle identities

Q: Use reference angles to find the exact value of the expression cos 3π/4. Do not use a calculator.

A: The given angle is in second quadrant, and the value of cosine is negative in second quadrant.

Q: Evaluate (5cos 60° +4 sec 30° – tan 45°) (sin' 30° + cos 30°)

A: We know that cos60°=1/2 , sec30°=2/√3 , tan45°=1 , sin30°=1/2 , cos30°=√3/2

Q: Use a sum or difference formula to find the exact value of the expression sin 195°.

A: Calculation: The given expression is sin195°. Use the sum formula to find the value of the given…

Q: Without using calculator, find the value of the following Cos 75 , Sin Sin . Cos Tan 105 12 12

A:

Q: evaluate cos theta when sin theta = -7/8 and theta is in the IV quadurant.

A:

Fundamentals of Trigonometric Identities

Trigonometric Identities are the equalities that involve trigonometry functions and hold for all the values of variables given in the equation.