Answer:
x ≈ 263.1
Step-by-step explanation:
The marked sides are the hypotenuse and the side adjacent to the given angle. The relevant trig relation is ...
Cos = Adjacent/Hypotenuse
cos(70°) = 90/x . . . . use given values
x = 90/cos(70°) . . . . multiply by x/cos(70°)
x ≈ 263.1
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Additional comment
The mnemonic SOH CAH TOA is intended to remind you of the primary trig relations:
Sin = Opposite/Hypotenuse
Cos = Adjacent/Hypotenuse
Tan = Opposite/Adjacent
